Thank you for your question and for your update asking about CSS modifications. Responsive design of image galleries has been a recurring and frustrating topic, starting some years back:
Gallery layout/responsiveness
WordPress theme and MLA styling
This topic links to three additional topics:
Variable gallery columns
And:
Vary number of gallery columns to fit page width
Responsive Images
My friend and MLA user Alexander Kunz just posted:
WordPress, Galleries, Mobile, Responsiveness,?AMP?!
In short, I regret that I have not yet found a great answer to your question. The guidance in the earlier topics can be summarized as:
- You can use MLA’s custom style and markup templates to replace the WordPress-like layout with anything that better fits your theme and/or meets your needs.
- You can use MLA’s support for other gallery-generating shortcodes/plugins to combine MLA’s data selection features with the formatting features of another gallery-generating solution.
I am marking this topic resolved simply because I’ve given all the help I can. If you find a solution you like I encourage you to post it here so I and other MLA users can benefit from the progress you make. Thanks for your understanding and your interest in the plugin.