I believe he is talking about sight paralax and it happens with a bow just like a gun.When you aim a gun or bow at a target,it is pointed upward(bullets don't rise).If your bow is sighted at 20 yards,you will most likely be at the highest point at 10-11 yards but every setup will vary.
To the first question,you will most likely not see a change in your sights untill you get past 30 yards with a 10 pound increase in draw weight.Maybe a little sooner if you are a really good shot.
