Can anyone tell me if these need to be plugged in to a computer to mine. If i can use the computer to set it up and leave it mining by itself that would be great
I would suggest you run the proxy on a raspberry pi instead. Runs great 24/7. This way you dont have to keep your PC up all the time.
I tried Minepeon with a Raspberry and my rejected share rate was significantly higher. I think if you use bfgminer and Raspian it might work better(?). I dunno, for me there were problems using anything other than Slush's proxy, something to do with long poll support and the cubes, even bfgminer as proxy on PC wasn't allowing long poll support. Fwiw, you might want to check the rejected shares in the cube webUI.
I run it with bfgminer as proxy on raspbian. It turns out to be run fine for me. The rejected shares stay around 0.03% all the time.