Nerdbox can work with any USB controller. Simply plug it in, and configure it using the onscreen menu. More details on controller configuration can be found here. Nerdbox also supports Bluetooth controllers or wireless controllers that use a USB dongle. Nerdbox ships with two SNES controllers, as I love playing with friends!
Yes, you can play 4 player NES and SNES games! More info on setting that up can be found here.
Yes, you can use a USB mouse! More info on setting that up can be found here.
The SNES style controller looks a lot like the controllers originally used with the classic Super Nintendo Entertainment System. Directional pad, two shoulder buttons, four standard buttons, and a start and select. Probably the most functional controller for all systems.
A guide for configuring your own controllers can be found here.