Being a racial minority in any prison population requires the same fundamental skills that determine how anyone survives inside, and the core of all of it is respect.
If your ex grew up in the hood and understands street culture, he already has the most important tool available to him. Prison social dynamics are built on the same foundation as street dynamics in many ways. Knowing how to carry yourself, how to give and receive respect, how to read a room, and how to stay out of situations that are not yours are skills that translate directly from the street to the yard.
The racial dynamics in Georgia state facilities are real but they are also more nuanced than most people on the outside assume. Racial groups do tend to cluster, particularly around gangs, but tolerance between races in the general population has evolved significantly. An individual who is not affiliated with a gang and carries himself with genuine respect for everyone around him is generally going to be received reasonably well regardless of his race.
The gang question is the more important one. If he is white and unaffiliated, that actually works in his favor in certain environments. Being independent and clearly not gang-connected signals that he is not a threat to anyone's turf or operations, which removes one of the primary sources of racial tension in prison settings.
The rules are consistent regardless of race. Mind your own business. Stay out of other people's conflicts. Show respect and expect it in return. Do not try to be something you are not, but do not apologize for who you are either. Someone who grew up in the hood and knows how to navigate those dynamics has a better foundation than most people walking in for the first time.