Start of downswing- hips or shoulders first?

Go stand in a field, address an iron, swing it to the top then throw it underhand down the field. Whatever you did do the same when you hit the ball.

Spot on ! Right hand takes it back right hand brings it through
Everything stays synced, and your accuracy is good and consistent

Swing with your hips, your legs and whilst you will hit some phenomenal shots, your accuracy will be far less consistent

I know teh majority on here will disagree, but to my mind, simple is best
Unfortunatley, however this simple and accurate technique doesnt allow me to hit 300 yard drives