The buffer helps eliminate bolt bounce back. The buffer acts like a dead-blow hammer, when the bolt slams forward; just before it locks into battery; the weights in the buffer slam forward to keep the bolt from bouncing back, giving the locking lugs time to lock into battery.

Cycling / timing problems can be caused by a number of different things, such as weak springs, poor ammunition, dirty weapon, to name a few.

I don't think you would ever notice a difference in recoil from 1 weight to another.