Your main increases in draw length should come from keeping your upper torso straight rather than hunched over, your head upright rather than bent forward, good shoulder alignment, and getting your elbow back behind the arrow rather than short drawing the bow.
You should take full advantage of the grip geometry of the handle rather than using an artificially high wrist. The pressure of the bow should be against the same part of your hand each time you shoot. If you press against the bottom of your hand one shot and the bridge between your thumb and forefinger the next, it will affect the relative bends of the top and bottom limbs, and cause erratic arrow flight.
If you like more of a straight wrist, you can get a bow with a high wrist grip, but your hand should still make contact with the contour of the grip, so your hand won't be entirely straight, as it would be if you were pointing at something. Most people find that they shoot better and more consistently with a medium grip, rather than a high grip. Very few people find that they shoot better with a completely straight wrist where the only contact with the hand is at the bridge between the thumb and forefinger, unless they are shooting a relatively low weight bow. However, "very few" isn't none, so you owe it to yourself to experiment until you find what works best for you.