Your left hand position on the top of the backswing has NOTHING to do with your swing plane. The club only moves on plane below your hips, on the top, it deviates from the plane, the difference between Woods and Kuchar (or Hogan) is how much the deviation is.
Your plane angle should be determined by the club lie angle, so with the same club you cannot change the steepness of your plane randomly. What you can change is how the club wraps around your body (higher left arm makes it easier to wrap around for more power), thus giving people the impression of "steep" or "flat" planes. A book titled Decoding the Golf Swing Plane explains these things very well.