Replacing Logo with Text and then Control Font size and Add Tagline

Hi ,
In another support thread I was given this information to change my site title to text:
Please add following code to Quick CSS in Enfold theme options under General Styling tab

.logo img { display: none !important; }

And this:
then add following code to Functions.php file in Appearance > Editor

add_filter(‘avf_logo_subtext’, ‘kriesi_logo_addition’);
function kriesi_logo_addition($sub) {
$sub .= “Company Name”;
return $sub;
}

And I changed “company name; to my title.

And it worked. Thank you.

But I want to be able to control the font size and add a tagline.
So I found the following page:
https://kriesi.at/documentation/enfold/add-subtext-to-logo-replace-logo-with-site-title/

Is the code on that page what I would add to Functions.php to accomplish this? Which part?

There was also code in this support question that seems it might address the font control or a lack of responsiveness in smartphone rendering if I do this?
https://kriesi.at/support/topic/text-instead-of-logo-in-header-2/
This reply from Guenni007 seemed possible : Reply #486471
or this one:
From Rikard , reply #669671

Would adding any of those accomplish what I want? And to the Quick CSS or functions. php? And would I remove what I already put in?
And most IMPORTANTLY, will an update overwrite what I put in the functions.php.? Should I start all over with a child theme?

Thanks for your help and patience with me.
Stephan