just for understanding – these are the default values from loop-author.php:

// Default arguments for Author Loop
$default_args = array(
    'type'              => 'grid',
    'columns'           => 4,
    'items'             => get_option('posts_per_page', 12), // WordPress setting, fallback: 12
    'contents'          => 'excerpt_read_more',
    'preview_mode'      => 'auto',
    'image_size'        => 'portfolio',
    'paginate'          => 'no',
    'class'             => '',
    'show_modified_date' => 'no',  // 'yes' or 'no' - shows "Updated: XX" if post was modified
    'orderby'           => 'date',  // 'date', 'modified', 'title', 'rand', 'comment_count', 'menu_order'
    'order'             => 'DESC',  // 'DESC' (newest first) or 'ASC' (oldest first)
    'fallback_image'    => 'placeholder',      //  'placeholder'  or URL to fallback image 
    'post_types'        => array('post'), // Array: array('post'), array('portfolio'), or array('post', 'portfolio')
);

// Content Options for 'contents' parameter:
    // 'title'                  - Title only
    // 'title_read_more'        - Title and Read More button
    // 'only_excerpt'           - Excerpt only (no title)
    // 'only_excerpt_read_more' - Excerpt and Read More button (no title)
    // 'excerpt'                - Title and Excerpt
    // 'excerpt_read_more'      - Title, Excerpt and Read More button (default)

if you like to have it this way (grid, 4columns, exerpt with readmore, only posts ordered by date – newest first) you do not need to set the filter.
Then only the second part is needed inside functions.php.

The filter could do more – you can even differ between authors – f.e by author name. :

// 1. Layout for different authors by ID
add_filter( 'avf_author_loop_args', function( $atts, $context ) {
    if( $context == 'author' ) {
        // Common settings for all author pages
        $atts['items']             = -1;
        $atts['image_size']        = 'gallery';
        $atts['contents']          = 'excerpt_read_more';
        $atts['post_types']         = array('post', 'portfolio'); 
		
	// Fallback-Image from Media Library (Attachment-ID)
        $fallback_id = 2052;  // Your image ID from Media Library
        $fallback_img = wp_get_attachment_image_src($fallback_id, $atts['image_size']);
        $atts['fallback_image'] = $fallback_img ? $fallback_img[0] : 'placeholder';
        
        $author_slug = get_query_var( 'author_name' );

        // Individual configuration for a specific author
        if( $author_slug == 'guenni007' ) {
            $atts['type']              = 'grid';
            $atts['columns']           = 3;
        } 
        else {
            // default setting for the rest
            $atts['type']              = 'list';
        }
    }
    return $atts;
}, 10, 2);

the fallback image i get from media-library with the attachment ID
Advantage of this solution – the fallback image is based on the selected image size setting.

see:
grid for guenni007: https://basis.webers-testseite.de/author/guenni007/
list for johndoe: https://basis.webers-testseite.de/author/johndoe/

now my final solution is – to upload 3 files to the child-theme includes folder:

/wp-content/themes/enfold-child/
└── includes/
  └── loop-author.php ← PHP Loop (loads the css once)
  └── loop-about-author.php
  └── loop-author.css ← all Styles (Grid + List)

loop-author.php: https://pastebin.com/yaXj5Zfw
loop-about.php: https://pastebin.com/QQ84LGaw
loop-author.css: https://pastebin.com/zTJMtth9

to style the author page now are two entries for child-theme functions.php

// 1. Configure layout and settings
add_filter( 'avf_author_loop_args', function( $atts, $context ) {
    if( $context == 'author' ) {
        $atts['type']              = 'list';               // 'grid' or 'list' Layout
        $atts['columns']           = 4;                    // columns count
        $atts['image_size']        = 'gallery';            //  image-size
        $atts['contents']          = 'excerpt_read_more';  // Content-Type
        $atts['items']             = -1;                   // Posts per page
        $atts['paginate']          = 'no';                // Pagination  on/off  (yes or no)
        $atts['show_modified_date'] = 'yes';               // 'yes' = shows  "Updated: XX"
        $atts['orderby']           = 'date';               // orderby : 'date', 'modified', 'title', 'rand', 'comment_count'
        $atts['order']             = 'DESC';               // order: 'DESC' (newest or Z-A) or 'ASC' (oldest or A-Z)
	$atts['fallback_image']     = get_stylesheet_directory_uri() . '/includes/fallback.jpg';  // an url or  'placeholder'
	$atts['post_types'] 		= array('post', 'portfolio');    	// 	count posts or portfolios or both
    }
    return $atts;
}, 10, 2);

// 2.  IMPORTANT: Customise query for pagination, sorting and post types
add_action( 'pre_get_posts', function( $query ) {
    if( ! is_admin() && $query->is_main_query() && is_author() ) {
        // Get the filtered arguments from above
        $default_args = array(
            'items'      => get_option('posts_per_page', 12),
            'orderby'    => 'date',
            'order'      => 'DESC',
            'post_types' => array('post')
        );
        $atts = apply_filters( 'avf_author_loop_args', $default_args, 'author' );
        
        // Set Query-Parameters
        $query->set( 'posts_per_page', $atts['items'] );
        $query->set( 'orderby', $atts['orderby'] );
        $query->set( 'order', $atts['order'] );
        
        // Set post types - IMPORTANT: even if there is only one type
        if( ! empty( $atts['post_types'] ) && is_array( $atts['post_types'] ) ) {
            // WordPress requires 'any' or an array with multiple types
            if( count( $atts['post_types'] ) == 1 ) {
                $query->set( 'post_type', $atts['post_types'][0] );
            } else {
                $query->set( 'post_type', $atts['post_types'] );
            }
        }
    }
}, 999 );

see result page : https://basis.webers-testseite.de/author/guenni007/
Unfortunately, no translation for But we are proud to say that %s contributed %s entries already. has been added to the (at least German) lang files yet. That is why it is in English on my example page.

i tested all 3 blog styles – it works on all of them.

i’m participant as you are – so i do not see any private content area.

on general layout – Maximum Container Width – this is the value i pull out in the snippet for the setting

$responsive_size = avia_get_option('responsive_size');

If you have there a 100% width set – then it wil be synchronized in the snippet too.
If that is the case – you have to use the other snippet with the “hard-coded” width and replace th 1310px with your 1400px now:

function grid_layout_notfull(){
?>
<script>
(function($){
	$('.av-layout-grid-container.grid-notfull' ).each(function() {
		var notfullID = $(this).attr('id');
		$(this).hasClass('main_color') ? $(this).wrap('<div class="main_color notfullsize '+notfullID+'"></div>') : '';
		$(this).hasClass('alternate_color') ? $(this).wrap( '<div class="alternate_color notfullsize '+notfullID+'"></div>') : '';
	});
	$('.notfullsize').css({"clear": "both", "width": "100%" , "float": "left" , "position": "static" , "min-height": "100px" });
	$('.grid-notfull').css({"max-width": "1400px", "margin": "0 auto" , "padding": "0 50px"});
})(jQuery);
</script>
<?php
}
add_action('wp_footer', 'grid_layout_notfull');

can we influence the image shown in the ajax preview ( that img insided avia-gallery-big ) – it seems to use the recalculated “large” image.
But as you know this might be bigger in file size than the original uploaded image!
I can not find a filter to adjust it.

or could we influence it by
$params['preview_size'] = apply_filters( 'avf_ajax_preview_image_size', 'gallery' );

i can find this in portfolio.php

//	create array with responsive info for lightbox
	$img = Av_Responsive_Images()->responsive_image_src( $attachment->ID, 'large' );

bring it to full will often reduce file-size – as you know that Enfold standard compression leads to bigger file-sizes on large image.

ok – i found the place to change in gallery.php (line 757)
$prev = wp_get_attachment_image_src( $attachment->ID, $preview_size );

if we would use :
$prev = wp_get_attachment_image_src( $attachment->ID, 'full' );

looking to his page f.e.:
the krebs-treppen-systeme-gelaender-system30-3.jpg is 121kb
but krebs-treppen-systeme-gelaender-system30-3-1030×839.jpg is 268kb

the whole page got over 112MB images – and could be reduced to a half size.

you can find the defintions of standard icons on enfold/includes/config-enfold/init-base-data.php

Easy Slider is on default using:

'svg__next_big'  	=> array( 'font' => 'svg_entypo-fontello', 'icon' => 'right-open-big' ),
'svg__prev_big'  	=> array( 'font' => 'svg_entypo-fontello', 'icon' => 'left-open-big' ),

The Filter you can use to change these icons is: avf_default_icons

you can use it like this in your child-theme functions.php:

function avia_replace_default_icons($icons){
// e.g.: changed by uploaded svg files - using the ID's and the font-name is svg_wp-media-library
	$icons['svg__prev_big'] =  array( 'font' =>'svg_wp-media-library', 'icon' => '50913');
	$icons['svg__next_big'] =  array( 'font' =>'svg_wp-media-library', 'icon' => '50591');     
	return $icons;
}
add_filter('avf_default_icons','avia_replace_default_icons', 10, 1);

but: What is the font-name of your uploaded icon-set

you find that information on :

now f.e. if you like to replace these standard icons by icons of the iconset : medical

function avia_replace_default_icons($icons){
	$icons['svg__prev_big'] =  array( 'font' =>'medical', 'icon' => 'uf101');
	$icons['svg__next_big'] =  array( 'font' =>'medical', 'icon' => 'uf135');     
	return $icons;
}
add_filter('avf_default_icons','avia_replace_default_icons', 10, 1);

you can find those font icon codes f.e. on trying to place that icon you like to have and hover it :
( it is the value inside the brackets – without that backslash)

Edit: here is the solution with working separators on those color-sections

the color-section that should react like this:
give a custom class to it: av-video-section
give a background-color to it that does not disturb your video switch (not white – something that fits to your video content
place a codeblock element on top of your color-section ( codeblock to content – not as codesnippet)

<video class="responsive-background-video" 
        autoplay muted loop playsinline
        data-video-mobile="path/to/mobile.mp4"
        data-video-desktop="path/to/desktop.mp4">
    <source src="" type="video/mp4">
</video>

this to your quick css:

.responsive #top #wrap_all .avia-section.av-video-section {
  position: relative;
  overflow: hidden; 
  min-height: initial; /* taken from Enfold section setting  */
}
.responsive #top #wrap_all .avia-section.av-video-section .container {
  position: relative;
  z-index: 1;
  max-width: 100% !important;
  width: 100% !important;
  padding: 0 !important;
}  
.responsive #top #wrap_all .avia-section.av-video-section .responsive-background-video {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  object-fit: cover !important;
  z-index: 0;
  min-height: inherit; /* transfer from Enfold section setting  */
}
.responsive #top #wrap_all .avia-section.av-video-section .avia-divider-svg {
  z-index:2;
}
.responsive #top #wrap_all .avia-section.av-video-section .avia-divider-svg.avia-to-front {
  z-index:100;
}

the snippet for child-theme functions.php

function custom_responsive_background_video_script() {
?>
<script>
(function($) {
    "use strict";

    $(document).ready(function() {
        $('.responsive-background-video').each(function() {
            const video = this;
            const $video = $(video);
            const source = video.querySelector('source');
            const win = $(window);
            
            // Get video paths from data attributes
            const mobileVideo = $video.data('video-mobile');
            const desktopVideo = $video.data('video-desktop');
            
            if (!mobileVideo || !desktopVideo) return;
            
            function updateVideoSource() {
                const isMobile = win.width() < 768;
                const newSrc = isMobile ? mobileVideo : desktopVideo;
                
                if (source.src.indexOf(newSrc) === -1) {
                    source.src = newSrc;
                    video.load();
                }
            }
            
            // Initial load
            updateVideoSource();
            
            // Resize handling
            win.on('debouncedresize', updateVideoSource);
        });
    });
})(jQuery);
</script>
<?php
}
add_action('wp_footer', 'custom_responsive_background_video_script', 999);

see example page with divider : https://webers-testseite.de/background-video/