I have shot many old and new K Mags and Super Mags.
I have pulled them on scale to measure stacking. If you pull 29" you get about 1-1.5 lb more in that inch between 28-29" draw.
The old and the new ones both shoot similar speeds in chronograph.
Finger pinch- yes, as in most short bows. Finger will get use to it, but I added a thin aluminum liner to the inside of my shooting glove, all pinch and pain stopped.
I have learned the hard way, do not shoot arrows that are too light. Short limbs, long draw and light arrows will result in limb failure.