The longer the brace height the quicker the arrow gets off the string
I really do not believe this to be a major factor (if a factor at all in accuracy)
Some of the toughest to shoot - fasted bows around get the arrow off the string in 1/2 the time of the most forgiving target bows.
If this where the case IMO Top pros would not be shooting 500 to 600 grn arrows at slow mo speeds. They would all be shooting the lightest fastest arrows they could.