I understand that there is probably a significant amount of variation within the region, but to be more specific I would have to specify a specific country or region, and I have none in particular in mind.
So would nearby religions be 'related'? To what extent are they religions as the West knows; do they feature Gods? Are they similar to the 'pagan' religions of pre-Christian Europe (Norse, Celtic..)
Also, how large an area is each religion 'confined' to? Would they make up 1000 people? 1,000,000? Are there any indigenous religions which can be found throughout the continent?
Note: I posted this about a month ago, but got no response. I'm quite interested, so I thought I'd try again.
There are Africanists here that can answer, but you should definitely also go to /r/AskAnthropology, which has several people who do fieldwork in Africa.