It always depends on the individual case. As a rule, they are just as good. You should just make sure that the accessories are included. By that I also mean a WLAN antenna

That's difficult to say. I bought new ones.
But you have a warranty from Galaxis, so why not?

I can't tell you, I don't have a comparison.

I was completely satisfied, the box had signs of use, the item had none. If you do, pay attention to the accessories.