Luffy DF have crazy potential , there's no way Oda would make Luffy reaching top tier status be " let's add lightning effects to his punches"
Kaido can use elements like fire and lightning, is implied to have regeneration, he could use his flame clouds...ect
Fuji with his DF and being Top tier should mean he have island lvl DC when he's fighting at full powers, that's the expectations set for top tiers
right now Luffy and Kaido look like high tiers at best lol there's no way this is what peak strength in OP look like