My question is: what exactly does it clone? Is it just the FIDs (/drive?/fids), FIDs+config (/drive?/fids + /drive0/var), FIDs+config+all user directories (/drive?/*) or everything on the player including metadata?

I haven't checked, but I believe it just clones the FIDs. Cloning the config is a bad idea as it contains, for instance, the player's name and static IP address.

Peter