The right leg should drive forwards towards the target with the release and post impact. So why do a lot of golfers early extend and pop the right leg out towards the ball? Learn the magic of the right leg here in this video. You may even learn the Greg Norman- Scottie Scheffler shuffle.
We are often led to believe that there is one ball position and one alignment for every golfer. This is a fallacy, and this video will prove it.
The drill one 430 path drill stops the right arm from straightening- allows the body to open and turn- and keeps the golfer pushing force into the ground through the feet and legs. It also sets up the drill three post impact that keeps pressuring the shaft to the finish.
The end of the club is hidden by the hands but here is a visual drill that can help the golfer see and feel where the shaft should align to create consistent strikes on the ball. 
The golf club only stays on the target line for a short amount of time. It does however need to enter and exit in a manner that will spit the ball out straight and eliminate curvature. Here is a visual to how it works.
Swing plane is not as mysterious as many believe it to be. Being great at the exit plane will help clear up and downswing difficulties. It's better to know where you are going than where you are going or even coming from.