Yes with 50 amps I use 2mm and with 40 I use te 1.6.I'll be doing a full write up, but I got the new welder, unboxed it, and set it up. The short version: whoa. I did't know how gutless my old welder was! At 50A I'm getting full welds and blowing holes in things! I've got more learning to do ;-)
For thinner, that works easier, but as you do it right, then 2 ad 50 amps will work fine. You ony need to watchout that you don't stay in to long.