SHARED ALBUMS / libraries to CONSOLIDATE pics

Either tool could be used that way, but each has limitations.

Shared Album limitations have to do with resolution of photos, length of videos, loss of metadata, number of items per Shared Album, and total number of Shared Albums (among other considerations).

The Shared Library has none of those limitations, but you can only own/join one at a time. It also does not have any internal structure of its own; each user owning/joining it has to maintain the structure in its Private Library, which is not visible to other users.