Can I sync folders in two devices over Bluetooth?
Well I can't really say &quot;sync&quot; but the closest tool you can use is : Bluetooth File Transfer.
Its free (with ads) with option of non ad version at a price, but still good enough for the former option.

It allows you to use your smartphone to browse, explore and manage
files of any Bluetooth ready device, using File Transfer Profile (FTP)
and Object Push Profile (OPP): you can also receive files and send
contacts!

It provides its own OBEX layer, additionally you can cut, copy, move, paste, delete multiple items using the integrated explorer of this application.