Deep East TX is most definitely not just the south, but the deep south. It's culturally no different from the Louisiana side of the border. Nacagdoches, TX --> Natchitoches, LA share more culture and history with each other than they do with other parts of their respective states going all the way back to colonial times.
SETX(from the golden triange to houston) like others have mentioned are easily apart of the southern gulf coast "western creole" cultural sphere especially as it pertains to Afr'Ams. The cooking, the architecture(shotgun houses), the geography, the music, the accents all fall squarely into that category. Remember, Juneteenth was created here.
And even central TX is historically apart of the "western" south. There are numerous historial freedmen settlements in the Austin metro area. And slaves even built the state capitol building in Austin.
And the black cowboy tradition in TX has more Florida, Louisiana, and Carolina roots than Mexican roots.
East TX BBQ
Barbecue in Texas - Wikipedia
More specifically SETX BBQ.
The boundaries of Southeast Texas barbecue
