I believe archery WPF improves draw speed and accuracy. I've not had more than 150 and 6 Powerdraw so I don't know how much things improve from there. After retiring, I'm now at about 129 WPF, too with 6 PD and really miss the 150.
It's also been said, ideally, to have 2 more powerdraw than what the bow requires for better results. With 6 PD and using a 4 PD bow I had more pull time before the reticule would start spreading out.
So, there's a balance between STR and AGI to fit the points where it seems fit. You can be more accurate with higher AGI and WPF, but with a weaker shot, or have a less accurate but stronger damage with higher PD.