Creating staggered scrolling gallery homepage that links to galleries

Site URL: http://pugmi.re/

Hello,

I'd like to simplify my photography website with a quick staggered-scrolling-overview which links to separate galleries/projects. This overview should ideally display images in various formats without cropping/reformatting to standard format e.g. 1:1.

Ideally I'd like to tweak an existing template to create this effect. I've been using Wells template for about 7 years and haven't seen any exciting new Squarespace templates for a while. I'm running a test site on Flatiron which seems to be the closest to what I'm looking for in terms of visual navigation.

Additionally, I'd like to be able to filter the main index/overview by category/tag. So, clicking on e.g. travel in the navigation bar would then show a thumbnail overview all travel-related projects, and filter out the rest. So far I've only been able to create folders with dropdown menus (using tagged links). Surely it must be possible to either filter out the main index, or create sub-indexes that link to (some of) the same pages as the main index?

Here are some good examples (but built with Semplice).
http://www.lindabrownlee.com/ 
https://www.juliushirtzberger.com/
http://caitoppermann.com/

Any tips would be appreciated. I'd obviously prefer to stay with Squarespace rather than moving over to Semplice. 

Cheers!
Christopher