If Duplicate Boy is limited to only using Domino's luck powers then Domino wins by just simply shooting otherwise Duplicate Boy wins. Luck doesn't really have much of an effect in a featureless environment. Although can ricochet projectiles off the ground and hit the target or jammed guns resorting to h2h. But I think luck really just cancels luck. Domino did study from Shang-Chi and learn how to somewhat consciously control her luck powers.