The biggest impact on left yaw, caused by the engine, is at high power and low airspeeds - an example is during take off. As the plane accelerates, picks up speed, the impact is reduced. The answer to your question is that the amount of right rudder needed to keep the ball in the center is continually changing with changes with power and airspeed. Neither approach will be correct all of the time either in combination or alone. If you mixed enough rudder to keep your tracking straight on take off then it would be yawed to the right once in the air with increased airspeed.

Howard