Should work with most devices that accept Bluetooth, see the 8bitdo website for pairing instructions. I tested it with a Nintendo Switch and it worked great. Obviously won't work with a Sega Genesis without a seperate adapter.
Can be used with master system as well. MODE+START+B. MODE+START+C. Golden Axe II, for example. Hold MODE+X+Y+Z until led went out. All compatibility modes (combo 3 and 4) will resets to default after power cycle on receiver.