Hello, it really depends on your investments, if your atk is high enough, then its definitely not needed and yes it can be used for level 3 without the ship :)
hey man, try Kizuna brook with mr 3 attached to him, use his special stage 4, and use rayleigh or corazon on luffy/law, the damage will be tight though because you won't have wano orbs, and the resistance down. You can also enter stage 4 as law and swap into luffy to do more damage though. Good luck