I'm not sure about the specifics for some where like the congo but I'm more aware about politics of west and east africa then central africa. For the first example the fulani people are wide spread ethnic group in africa (mainly in the west) and it's common for african americans to descend from them because they used to be slave raiders and in exchange many ethnic groups rose up against them and sold them to europeans. But anyway Sunni Ali of the songhai empire committed genocide against these people to kind of extreme (all genocide is extreme) and had fulani that he went to battle with hanged, during this one battle he had hundreds of the fulani war prisoners hanged (based on the stories he seemed pretty terrible and had a lot people killed in general and some historians thinks that this was propaganda and others believe he had bipolar personality disorder) but he a general disgust for these people specifically. The hausa people had city states which were territories of the songhai and pretty much assimilated their culture and looked down on the fulani but hundreds years later the fulani committed jihad's against the hausa and the fulani became superior class for awhile. The hausa had traveled to west africa around 1000 and named their neighbors and the names kind of stuck like the name the yoruba and it was originally yariba which meant "shady and unreliable" and the hausa also named the fulani. Sunni Ali controlled the songhai empire by pretty much mass killing of people of other ethnic groups. His successor Askia Mohammed brought peace to all the ethnic groups under the songhai empire. If you were fulani you wouldn't necessarily be liked but a person wouldn't be committing genocide against you.

On the east side of the continent the abyssinian empire (mainly amhara people) basically did the oromo people how europeans did to any native people. Like they pushed them out of their land and took it over then the abyssinian raid their remaining villages and sold a lot of them to egypt and then would be sold probably the ottomans. Sense ethiopia was never colonized the amhara remained in control over the oromo and they were treaty like second class citizens. Like in more modern day from 1941 to 1991 they weren't allowed to speak their language in public and amhara language and culture was forced upon them. Like the oromo used to be called galla which is there equivalent to the n word. They had protest last about political injustice against their people back in ethiopia.

In southern africa I'm not very aware of the relationship but I do know that with the bantu expansion the bantu pushed khoisan/san bushman people (the oldest ethnic group in the world) out of their land which they inhabited for the last 20,000 years. Some people believe through violence and others believe through having a bigger population and just over running them. When europeans first arrived to south africa the bantu ethnic groups told the europeans that they weren't of the same race and so from this the difference in phenotype led this to be the only time europeans went to africa and not consider someone black. There's still some conflict between the San and the bantus living there over who's land it's rightfully is.

When not considering the amazigh and arabs and europeans in south africa. You can divide the 3,000 african ethnic groups in to pretty much 4 four larger ethnic groups or variations of african. Which are the bantu which are majority of africans and then there would be nilotic people who tend to be tall and they are the darkest skinned people in the world. Then there would be the cushitic people they mainly live in the horn of africa but there are some people with cushitic dna in other parts of east africa. Then there would be the khoisan/san bushman who are the oldest ethnic group in the world and they kinda have stereotypical asian features and they have the smallest population out of all of these with only a couple hundred thousand people left.

Africa over all has historically done things based on ones ethnic just like how people from any other continent would. So yeah hopefully my answer was good enough for you and sorry that I don't have enough knowledge on the congo.