The center USB port is for connecting to your computer/device, and the outer ports are actually a hub. You can connect other devices or daisy chain a bunch of macro pads if you're so inclined. :D
By the looks of the PCB, any standard Cherry style switch will work. This includes Holy Pandas of course. This PCB is also Hot-swappable which means the switches can be changed and replaced at any time if you do not like your first pick.