Grave's inital playthrough is enjoyable, albeit janky in the late game; once you unlock the final two characters expected in the endgame for replay value it's the most obscene mixed bag. Billy is by far the most enjoyable playthrough while Juji is entirely a slog and honestly painful to sit through in order to access the game's extra content.

Just play through it with Grave and then enjoy the smooth second playthrough with Billy; it's not worth the pain of the third playthrough for nothing but horde extras and minimaxing the gameplay for anything worth following through for the postgame goodies.