If I have 100gb of photos and videos on Google photos and I was paying for the storage, can I download or backup before removing? Other then only doing a few at a time.
The second question is easier, your pictures stay there and you can't add any more photos without upping the storage. Same thing with Google Drive, as they share that space.
As far as the downloading all photos, go to Google Takeout here: https://takeout.google.com/settings/takeout and you can download all your bookmarks, calendar stuff, drive files, photos, etc, etc. If all you want is photos and documents, you can just check those two things and uncheck everything else and go to town.