A quick fix that may help others.
By default, Enfold uses the 640×640 image for all sizes in the Instagram widget. In “framework/php/class-framework-widgets.php”
foreach ( $images as $image ) {
// see https://github.com/stevenschobert/instafeed.js/issues/549
$image['thumbnail_src'] = preg_replace( "/^https:/i", "", $image['thumbnail_src'] );
$image['thumbnail'] = $image['thumbnail_src'];
$image['small'] = $image['thumbnail_src'];
$image['large'] = $image['thumbnail_src'];
If like me you use Thumbnails in your widget, the 640×480 image causes an F on the PageSpeed rank. To get better sized images, replace
$image['thumbnail'] = $image['thumbnail_src'];
with
$image['thumbnail'] = $image['thumbnail_resources'][0]['src'];
This gets the 150×150 image url for the thumbnail.
Hope this helps someone.