#3 - YOU SHOULDN'T BEND YOUR LEFT ARM
Being shown that Jordan Spieth and Lee Westwood have a bent left arm doesn’t sell it to me. You don’t HAVE to have a straight left arm to play good golf.
If trying to do so limits the length of your backswing, reduces your wrist hinge dramatically or introduces so much tension that you either lose all swing speed or even worse, injure yourself, then don’t do it.
However, you should understand that a bent left arm will shorten the radius of the swing (or bring the club head closer to you) and this can easily cause you to top the ball.
So a straight left arm from setup to impact is preferable unless you start with a bent left arm or have some sort of drop during that time that is just the right amount to get the middle of the club face on the ball.