Baby Vegeta is just straight from GT with no alterations but his version of Goku Black has traveled through timelines to get Zenkais and apparently easily killed Vegeta, Trunks, and Goku (future Trunks arc) once he got back to Trunks's timeline. He can also use Super Saiyan 4 and also Super Saiyan Rose Kaioken x20, which is something BVB can use as well. Goku Black can also use a limited version of his Kai healing, and by spamming Kaioken and healing himself over and over he can get huge Zenkai boosts in a short period of time without even needing mortal injury.
Assuming GT Beerus isn't all that different from DBS Beerus, Baby Vegito Black can hold his own against Beerus at full power, and with Kaioken he completely dominated Beerus, forcing him to use his incomplete UI.
He also has access to the Time Ring, which also allows him to teleport himself slightly forward in time to dodge attacks.