I think that Sergio Garcia perfectly blends these two phenomena in his late downswing action and I think that his clubshaft moves perfectly on-plane between the P6 position and impact - see images 6, 7 and 8 of his downswing sequence.
A golfer needs to realise that his "mind" must be in his hands (specifically PP#3 of the right hand), and he must realise that he can keep his clubshaft on-plane during the downswing by acquiring "educated hands" that allow him to consistently trace the SPL using PP#3.
Instructors/Training – Perfect Swing Training Center
A golfer can definitely hit the ball further using two-arms, compared to using only the left arm alone, but only if the right arm is applying push-pressure at PP#1 in perfect synchrony with the left arm's grip-pulling action (due to an efficient pivot-induced release of PA#4).
Four keys to the perfect golf swing - The Boston Globe
Golfers who slice typically don't have enough "Down" in their down swing as they start back to the ball from the top of the back swing.
How to Perfect a Golf Swing | Healthfully
When a repeating swing takes form, a whole new level of satisfaction results as the golfer is now able to play the game the way it was intended.
Tiger Woods: The Perfect Golf Swing - YouTube
It doesn't matter whether you are trying to break 105 or 70, the rate of improvement is typically rapid once the "bad data" is stripped from a golfer, and The Key to a repeating golf swing can begin working its magic.
Every good hitter will do these 7 things on a perfect swing
The major source of swing power in the modern, total body golf swing is the pivot action, and a modern day golfer primarily uses his pivot-drive to power the swing.
Mike G. - A Perfect Swing Golf Group (Charlotte, NC) | …
If a golfer learns how to keep the clubshaft "on plane" during the downswing, while shallowing the clubshaft plane, then it will allow the clubhead to approach the ball along a shallow inside track, and eventually move in-to-square-to-in through impact.
The Perfect Golf Swing: Dispelling the Myth | Article | TPI
If the clubhead swingpath is in-to-square through impact, and the clubface is square at impact, then the ball should fly straight towards the target (presuming a level strike on the sweeetspot of the clubface).
*FREE* shipping on qualifying offers.
It is also possible to perform a downswing using a hitter's action or a right arm swinger's action, and they operate according to a different set of golf swing fundamentals.