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.
I get many comments about a video I made several years ago named "Out Is Down". Here is another example of it -with Patrick Reed- showing how hand path and club path are different.
Lag of the clubhead is an important benefit to releasing the club late in the swing and with power. Drill 4 is one of the training protocols in allowing our body to do such a thing.
The swing is an arc from an above and inside the ball view. The clubhead should travel along the target line for a few feet before it starts arcing back to the inside. Here is a drill to help achieve that.
The drifting and grabbing of the right foot is something I have discussed for over 15 years now and yet still most people do not understand it or know the pressures that help create it.