Releasing radial deviation early and its effects on speed

I haven't seen data, but my guess is very little. I think there would be a much bigger correlation between releasing the trail wrist extension and speed. I often see amateurs keep radial as long as pros, but rarely do they have the right trail wrist extension pattern.

The speed in the release comes mostly from the body combined with some help from the pronation/supination of the forearms. One tricky thing is most golfers don't feel speed accurately. For most golfers I work with, their fastest speed swings have to be calibrated. Initially, just swinging harder, or swinging harder from the wrong parts, doesn't result in faster clubhead speed.