Whether one is better than the other depends on how you want to work and if you have a choice. Some people don’t have network access for their controller so are forced to use the USB option. As I said, I use the network option.
I don’t know that I’ve seen anybody raising the feet with waste board material. I think you’d have to be careful about that as it may impact the stability of the CNC machine. You are adding extra leverage (kinda like a cheater bar on a wrench). I have seen some use of riser blocks on the Z gantry to do the same, but that also sparks discussion about what negative impact that may have on how solid the system now is. I really can’t advise one way or another as I have no experience.