Good idea but not sure Mylio - as currently designed - is a reasonable tool for this . It’s not a web site or a server.
Unless I’ve missed something, the basic premise in Mylio is that ALL photos are always synced to ALL devices. You can customize which SIZE photos get synced to which devices (thumb, preview, original) - even based on star ratings, keywords, color labels or size (but not Categories unfortunately). Regardless - ALL images will still get copied to every device, at least in thumbnail size.
It just doesn’t make much sense to copy ALL your images to someone else’s phone or computer, and then try to limit them to only viewing a small subset of them.
I really wish Mylio had something better suited for this - some kind of “publish & share to the cloud” feature. It makes zero sense for me to tell family members to install Mylio and sync all of my 300,000 photos to their phone - just so they can see a few hundred family or vacation photos.
So instead, I currently publish sets of photos to Google Photos, my SmugMug site, or elsewhere when I want to share them.