Question regarding corrupt iCloud photo/video library

Hi Everyone, not sure how it happened, but I realized last weekend that several thousand photos/videos were missing from iCloud.

My setup - iPhone and MacBook Photos apps are set to 'optimize storage'. MacMini Photos app set to 'download and store original' photos/videos.

iCloud has been turned off on my MacMini for two weeks (changed password, forgot to log back in). However, MacMini Photos app appears to have all photos/videos (complete library)!

My question - what happens when I log back into iCloud on the MacMini? Will it update iCloud and 'fill in the blanks' or will it remove the extra photos/videos from the MacMini not currently present in iCloud? Note - there are only a couple of items in my 'recently deleted' folder, none of which match the several thousand that are missing from iCloud.

Any advise would be appreciated!

Dave