If you are taking stuff from the masterclass book, may i suggest you try the first book, as this explains the premise behind the swings and the master class book re-affirms and breaks down in detail the study behind it.
Personally i dont think you should pigeon hole yourself into either, there is more than one way to skin the cat that is golf, and by setting yourself into a certain modality of swinging i think you may restrict your progress.
Getting back to your swing, there is a lot of extension in the early part of your golf swing this is at the expense of a natural wrist set whereby the weight of the club will set the angles naturally, by extending as much as you can you delay the set and because of this your right arm starts to creep behind you and this then sets the plane flat, your swing then lifts slightly but by this time your face is shut and your arms have swung too far, the dowswing is a great move but it is hampered by what has gone before, i am a great believer that what you put into your backswing is what your downswing will give you, so if you make bad moves back, there will be compensations coming down.
1. Work on the drill i suggested as it will get the takeaway more on line toi start and also encourage the correct shaft plane later in the backswing.
2.A good drill i suggested to EZ was get on your knees (stop it) get a club, grip down it, then make a backswing, this will restrict hip turn obviously and will shorten your arm swing and upper body coil, but when the backswing stops, that is your optimum swing length for arms and upper body coil, anything past that point in a normal swing would mean your turn is too much past your flexibility point, and your arms are losing connection with your body.