Three computers one Apple ID I have three Macs and one Apple ID.  If I remove a folder or individual photos from Photos on one computer, will it disappear on the others?  What's the best way to  manage this so each computer can be used independently?
If you delete a photo from iCloud Photo Library, it prompts you whether you're OK with the picture being deleted from all of your devices.

The best way is to each person to have their own Apple ID. If all the three macs are your personal machines, disconnect two of them from iCloud Photo Library and switch on Photo Stream, that way the two machines will get the new photos and you can delete the ones you don't need.