Your posture is determined by your arm swing. If you swing up and down on a two plane swing then you should stand more upright. If you swing your arms around on a one plane swing then stand more bent over on the balls of your feet.
Many golfers set up with their right side too high, your stance should look like a Reverse K with the left side straight and high
Control the distance of your chips and pitches by extending your backswing a little further as the shot gets longer