Looked at both plugins and I don't understand how either one would allow me to create a lightbox frame with mixed content that links to a gallery with a different thumbnail image.
The example of what I am trying to achieve should be fairly clear from the gallery that's included on this page: https://www.benjaminwallfisch.com/projects/ but have also attached two screenshots to explain.
First is of the page linked above with the gallery on this page that has custom thumbnails set for each of the different film posters.
Second has highlighted in red the lightbox that opens when you click the thumbnail and the lightbox has mixed content, a jpg, a few links, and a youtube video embed.
Are you sure that one of the plugins you recommended can achieve this and if so, can you please elaborate a bit on how? Happy to read through the documentation for both again but trying it out, at this point, I can't see how it would work.