You can do it either way. What I suggest though is to LEARN by drawing THEN bending. Later, when you are sure you know what the feel and position is that you want, you can draw AFTER bending.
Either way, there is going to be some movement and whether it comes before or after drawing, the movement will still be the same. Regardless, I still say that maintaining the 90 degree angle between the bow arm and the spine is important to a consistent shot. That is the point of the "bending at the waist" theory.
Arne