Because those two knobs affect the pitch of the blades (in different ways) they can either bog down the motor (too much pitch at low throttle) or go the other way and you won't have enough pitch and will be hovering at 90% stick. Having a bit more head speed is a good thing for tail authority but beyond affecting the pitch curve, and therefore the throttle, it doesn't affect the way the heli flies in terms of aileron and elevator. higher head speed will provide a snappier response though.