RE: draw weight
I forgot to add that I don't think it will change point of impact that much if any. Another thing that will effect that is how far away the sight is from your riser, and whether you use a peep sight and how you use it. I do a lot of playing with my bow and I rarely have to change my 20 and 30 yard setting. Even switching from heavy to light arrows. Once you get beyond 30 or 40 yards you may have to close the gap a bit on them.
I will explain the above statement. The farther away your sight is from the riser the larger your pin gap will become, but your adjustment will become more precise since you have to move your pins farther to get them where you need them. And normally if you use a peep sight your pin gaps will be closer. It really depends on how you use it though. If you center each pin in the peep at there respective yardarges you will have closer pin gaps. Essentially you are slightly changing your anchor point at each yardarge. You don't really notice until you get beyond 40 yards though. If you don't use a peep sight or use a no peep or something ismular your pin gap will be larger because you are not changing your anchor in slight amounts each time you move back. Same goes for if you center your sight housing in your peep instead of each pin. This works well if you have a large peep and not very many pins. However if you have a smaller peep and want to shoot beyond 40 yards this may not work to well, you won't get the sight picture you need.
And Tfox is also correct about the trajectory thing with rifles. The laws of gravity state that all objects fall at a steady rate. Bullets rising after you shoot them is an optical allusion of sorts because of the sight height. Change the height of your sight and trajectory will change.
Paul