Here are a few screenshots... should be self explanatory, and I bet a lot of you knew about this already. I just made a STF and started testing.
6 Power Draw, 140 Archery WPF
6 Power Draw, 172 Archery WPF
9 Power Draw, 130 Archery WPF
13 Power Draw, 115 Archery WPF
All of these screenshots were taken as accurate as the aim got, and right before they started widening (there was no holding the draw at that accuracy), except for the 13 Power Draw one which stays that accurate for a few seconds.
I'm pretty sure it's not supposed to be this way (13 Power Draw also drew the bow the fastest), and there is basically no other aim difference between the other 3 screenshots...