I would love to have more control over Plex sync.
As it stands, you cannot set a maximum storage used for sync files on the server. I have had my server’s hard drive fill up due to users syncing lots of files and not downloading them.
My suggestion is to offer settings to:
Set a maximum size for Plex sync folder
Set a maximum size for Plex sync files per user
Set a maximum time limit to keep Plex sync files, after the time is reached delete the files and prevent them from being automatically requested (if this is a thing?) by the user. They can of course manually request them again.