It will only mount one USB drive if you hook 2 up to the port. It is possible to mount the 2nd, but it involved rooting and a bunch of terminal commands.
If your USB drive has 2 ports, it needs the 2nd one for power. Using a hub will not increase the power output from the single port unless it is a powered (plugged into the wall) USB port.
It may work for xbox controllers, but you will have to test it out.