Conventional fitting these days is to play with the lightest most flexible shaft "that you can control". Homer (from the thread) says "Stiffer better".
I have fitted people with the view of 'that you can control' being the leading issue. If you are a swinger you can feel a lagging clubhead MORE with a whippy shaft as its still "way back there" vs a stiffer rod.
Yoda, what did Homer say about shaft Torque as that is all about the clubface twisting though impact and of course release too?
Players with better release mechanisms fit with stiffer shafts. Lesser golfing mortals generally feel more with a softer flex.
Torque wise same.
I personally like flexible shafts with low torque but I stress that is for my own clubs.
Hope that adds a bit of a twist to the to the conversation.