usb 2.0 or 3.0 it doesnt matter. it doesnt completely swamp usb 2.0 so there is no need for usb 3.0. you can however hook it up to a usb 3.0 port as they are backwards compatible with usb 2.0
for passthrough you would need to plug in another usb cable (2 total) into the back of your pc. afaik the passthrough is 2.0 only. again you could connect up to a usb 3.0 port but you're going to be limited to 2.0 speeds.