[kamandi]

For ball above feet, should we set up with a open stance, more steep plane since the slope will make the swing more around and will affect the low point?

I think, in the end, you gotta go with what feels right for you.

I haven't heard anyone mention this, so it's probably not the recommended set-up, but I actually set-up with a closed stance in ball-above-feet situations. I feel that the golf ball is pretty close to me, so I set up with the closed stance to help me with my turn, as well as to give myself space for my arms on the downswing. I just mess with the aim and the club face orientation to adjust direction.