Hi Sarah, did you have the chance to try and compare this plugin to the Meow Gallery? The Meow Gallery does also this (real-time preview, similar layouts, etc...) but also work with the classic editor and the shortcode.

We actually thought it was better to use a shortcode (created automatically by our Gutenberg block, so invisible to the user) so that the gallery output stays up to date, even if there is an update or a change in the system. With a Gutenberg "statically" generated gallery, you might have, one day, to go through all the pages where you used the block in order to refresh it.

I put a lot of thoughts into this for the past few months so I would be really interested in having yours as well.