Do I need a CSB ancient Faith study Bible if I’m already reading Eusebius?

That is up to you personally. Both works are great for understanding early Christian history and can be enjoyed for their own merit and content. Eusebius stands with Origen in scholarship, but the CSB covers a larger period of time which features study notes and commentary from the writings of the church fathers of the second through fifth centuries

i dont think i finished reading Eusebius, but all i had was one copy of a book. i doubt you need a study bible of any kind. its usually commentary on a particular view point. there are thousands of views and perspectives even those that debunk and invent lies about everything.

nope