I explained why iCloud is not a backup-- it backs up mistakes. Most of us think of a backup as a place to go when we accidentally (or stupidly) mess up something valuable. iCloud just copies the mess up.
A Smart Album offers a way to investigate which pictures are the culprits.
Your problem pictures have lost contact with the original files so, while you can see preview and thumbnail versions, there is nothing there to edit or export. This can happen if those originals were never copied into the Photos database, but Photos used exterior versions. (That's why I asked about the settings.) If those exterior originals are moved, then Photos has nothing to work with. Another possibility is that the Photos database became corrupted. This can happen when a "cleaner" type program is run-- those programs, like CleanMyMac, are notoriously destructive. There are other 3rd party apps that promise to do something with Photos, as well, and corruption can occur with someone just opening the Library Package and messing around inside.
If the originals are completely missing, then you would need to find those files in old backups and re-import them.
If the database is corrupted, then you may be able to repair it by rebuilding your Photos Library. To do this, close Photos and re-launch by option-command-clicking the Photos app icon. This may help, but you've lost quite a bit of data. I would consider disconnecting from iCloud before the repair and testing. If it works, and you reconnect iCloud, Photos will have to re-sync, and that might take days to weeks.
You mentioned having Time Machine and clones, so you may be able to find a Library from before the corruption, or you might find the original files that were somehow left out of the Library.
Good Luck. Let us know how it goes…
