I promise that our next version would have the option to set the thumbnail size from our settings page.
Kindly follow the steps below as a quick solution for this issue.
For Categories:
1. Kindly open the following file,
/wp-content/plugins/all-in-on-video-gallery/public/templates/category-thumbnail.php
2. Search for the line below,
$image_data = aiovg_get_image( $term->term_id, 'large', 'term', true );
3. Replace it as,
$image_data = aiovg_get_image( $term->term_id, 'thumbnail', 'term', true );
4. Save the changes and check now.
For Videos:
1. Kindly open the following file,
/wp-content/plugins/all-in-on-video-gallery/public/templates/video-thumbnail.php
2. Search for the line below,
$image_data = aiovg_get_image( $post->ID, 'large', 'post', true );
3. Replace it as,
$image_data = aiovg_get_image( $post->ID, 'thumbnail', 'post', true );
4. Save the changes and check now.
Hope this solved your issue!