I've been shooting a bow a long long time and IMO your bow arm should have a slight bend in it. Also your left wrist, if you're a right handed shooter should also be canted slightly. Experiment with your grip until you find which way you shoot best. When I shoot my left arm is slightly bent and the bow's grip sets between my thumb and index finger with my index and middle fingers loosely wrapped around the bow. (not holding it, just to keep it from falling after the shot. My ring and little fingers are curled into my hand and do not support the bow at all.
The key to shooting a bow is consistency. Find what works best for you and do it every time.