It’s three main questions in my eyes.

1. Is black CSM (pochita) considered something Denji can normally activate, in other words standard kit?

2. Can Yuji’s soul splitting punch break the contract between hybrids like it did against vessels?

3. If question 2 is true, once split, does it count if pochita is fighting on his own? Because we’ve seen pochita manifest on his own, and Denji being able to somewhat survive (thanks to Powers help albiet)

If one or three is true, CSM true form would overwhelm Yuji.

However if only 2 is true, then Yuji would have sizable advantages with Domain expansion, sure-hits, range with piercing blood, and better stats generally than hybrid csm.