Penitence + dlc content

I played through the game on the switch before and recently got it on steam, I never meddled with the penitence mode in ng+ so I figured I’d try it. I used the one on the left that lets you have regenerating fervor but also halves my sword damage (which I feel like is more than half but whatever). My question is, are all the dlc bosses really hard or not with a penitence? I fought the two new ones for the eyes on my normal file already one wasn’t too bad the other quite hard so I’m thinking if I should restart the run or not. Also do mea culpa shrines still buff my damage even tho I already have the skill tree filled from the initial run?