I just finished a speedrun of Cuphead where I got 300% (All coins/weapons/supers/charms + divine relic) while also getting a P rank on all run and gun stage and a S rank on all bosses. I was curious is this was a separate category from regular 300%.

No. 300% Does All of what you did, but fights all KD minibosses and disregards rank. Currently no speedrun that mimics what you’ve done.

There isnt one but if just the main game got one why doesn't the main game + DLC get one too?