I'm not quite sure what you are asking for here. How to play with the guitar on your right knee? Andreas also has pictures showing that on the link I provided.
Well, as I said, my suggestion for the most "ergonomically sound" (ie comfortable) seated guitar playing position is the classical one. You don't have to actually be PLAYING a classical guitar to use that position. YOu are allowed to use it with any style guitar
I don't recommend shifting from one positon to the other, but that's just me. Re; playing a dreadnaught on your right knee-you are combining the worst of both worlds-a position which forces your right elbow and shouder to ride up with a large guitar that will make it even worse. Having said that, many many folks do play the guitar that way.
Re; standing and playing-first you stand, then you play
. Guitar strap helps. Guitar angle and height is whatever is comfortable to you-though again, having the guitar in the same relative position it would be if you were seated in the classical position seems to me to be the way to go. Your right hand wrist won't be torqued towards the little finger and your left hand won't be forced into over-suppination and flexion (carpal tunnel syndrome provoker there) to reach the fretboard (as happens with the "guitar on the right knee" guitar position.)