Yes, as per ASME section IX.

The ideal qual coupon thickness, in my opinion, is actually that which will allow for the maximum allowable thickness for each process you intend on using. You need 3/4" deposit thickness to achieve the 8" max allowed for each process. For two processes this means 1 1/2" thick coupons. Getting thicker can give you more processes but it becomes rather unweildy from a test perspective and impractical from a cost perspective, especially for SS's. You can also qual your welders at the same time with the same coupon but I don't recommend it due to the reduced required thickness for performance quals, and positionality as an essential variable. If all you plan on qualifying is GTAW and FCAW then you can reduce the thickness considerably since I really cannot foresee the need to qual GTAW for 3/4".
The ideal performance qual, thickness, once again in my opinion, is a 6" XXS pipe in the 6G position. But you will generally need to qual with a smaller diameter pipe as well. 2" Sch 80/120/160 are the most popluar.