As far as distance, I dont even like to shoot 25 yards no matter what the poundage. At longer distances an otherwise perfect shot can go bad at the slightest flinch of the animal..but to each their own on that. Not trying to preach.
Shoot what you can. If you can shoot 100 pounds accurately and easily then you should. If you are overbowed and cant hit the side of a barn, definitely drop.
More weight is always better "IF IF IF IF" you can handle it fine.
But as these guys said, plenty of game has fallen to 40 pounds if thats what you accurately shoot.
Nothing wrong with lower weight if you can put a sharp broadhead where it belongs, but more weight is good when things go wrong.( bone hits, dense muscle, etc.)