From my brief experiences, anything past 20-25 yards for my bow and the more helical, the better. This is with field points.

What about broadhead blade alignment with the fletchings.

Shooting a prong rest, I can see the difference in the shot placement difference between the straight/1º and the radical helical arrows I have. The helical hit the prong as they go through, with cock down. Today I will try cock up and see what happens as this tread got me brain storming.