If I want to work on fast target shooting from the holster, its a Chapman/ISO blend. Elbows flexed slightly, support side foot very slightly forward. I focus on sight picture, sight alignment, trigger press, minimizing motion of shoulders, lower body, head, etc. At stationary targets.
But, truth be told, I spend most of my practice time shooting around, over, or under obstacles, from crouching, kneeling, prone, or supine positions, walking or running toward, away from, or at an angle to targets. When I can, I use moving targets.
When you do this, the differences between Weaver, Chapman, ISO, power ISO, or whatever else you might imagine, don't matter very much.