For sharing pictures in Photos Libraries, iCloud holds the Master Library, and all other connected devices are copies (complete or optimized) of the iCloud Photos Library.
iPhones and iPads use Photos to access their Libraries. But a Mac can have more than one Library! But only one of those, the System Library, can be connected to iCloud Photos.
So I have several Libraries on my Mac--an Old Family Pictures Library, a work Library, and so on. And I have a Library called Favorites with pictures that I have copied over from my other Libraries. This is my System Library, the one that I also see on my iPhone and iPad; it's the Library of pictures that I share with friends and family. I keep the System Library, which isn't so terribly big, in my Pictures folder on my Mac. Mostly I edit pictures in the other Libraries, and when I'm done, I copy them to Favorites.
Most of us who use multiple Libraries use the trusted 3rd party app PowerPhotos ($30) to help with copying and keeping the Libraries straight.
So that's how I do what I think you may want....