Not even worth crouching in an awp v awp peek. If you crouch, unless it brings part of your chest behind an impenetrable or thick enough wall, it reduces your hitbox size, but it makes proportionally more of it a kill shot. In addition, unless you're the one peeking, crouching sacrifices precious lines of pixels of kill shot hitbox in exchange for a slightly worse shot for your opponent, excluding corner peeking.
But that's arguing preference. I'd rather give a larger target to get a larger target than give a smaller one for a smaller one.