Changing tank to African cichlids??????

[kmny34]

So I have a 90 gallon freshwater community tank that I am going to change to a Tanganyikan Cichlid tank.

I am brand new at africans so anyone with any knowledge on Tanganyikans please feel free to help me out.

Substrate?
Can I keep my tank planted?
What other types of fish can I keep with Tanganyikans?
-I'd like to keep my 5 Denison barbs and Albino Bristlenose
Whats a good amount of Tanganyikans to have in a 90 gallon to keep aggression down?
Can I put any Tanganyikans mix together? Or do I have to choose certain breeds of Tanganyikans?

Please if u have any answers to my questions start with those! Any other suggestions are very welcome!!!

This will be a slow process so I have time to learn a ton about keeping Tanganyikans.