Contrary to what many people believe, most CA cichlids do quite well in high pH water. Many natural CA habitats experience wide seasonal swings in pH so the fish can handle it just fine. On average, a pH of close to 8.0 (or even a bit above that) is just fine for them, and of course africans do well in that water, also.
South American cichlids from the Amazon drainage (i.e. about 1/4 of the whole continent!) are the fish that prefer neutral to acidic water. However, even these fish that hobbyists purchase are most likely bred on farms where the water parameters would most likely not be the "natural" ideal.
Aggression is species specific. The T-bar is not known for being overly aggressive, but a sub-adult or adult fish won't take much crap before it gets irritated. What kind of africans are in with them?