Ngoma is in Kikongo and Mbonda in Lingala. The first recordlabel in Congo which was owned by a Greek businessman Nicolas Jéronimidis was called Ngoma. When a party or event is called Ngoma its often associated to traditional music. The name Ngoma got popular because of the way Kongo people in Leopoldville used to play it when their were funerals or traditional weddings with 8/9 persons and each drum having its own role. It was often impressing people. But nowadays it rare to see, its mostly in village. I once a saw in Bumbu a traditional band performing with ngongi and ngoma's and it sounded almost like Samba
Conga's normally don't exist in Congo. Each tribe has his own drums, but people tend to forget about it since moment Conga's got adopted in modern Congolese music. Folklore bands also adopting it replacing their traditional drums for conga's. Even those rare traditional flutes got replaced by keyboards. In my opinion Mbala-folklore got not authentic anymore the moment they replaced those accordions with keyboards. Accordions come from Europe, but it they were giving the folklore of Bambala special vibes. I am sure that they were also using flutes before it, like the way Mongo people were doing.
Few years ago Samuel Malonga wrote an interesting article about traditional drums, flutes, gitares, xylophones, etc.
https://www.mbokamosika.com/2022/09/les-instruments-des-musiques-traditionnelles-du-congo.htmlIts sad that they don't have a cultural policy in DRC, to preserve that cultural heritage, promote and teach people about it the way they do in Brazil, Mali, Senegal and Cuba. The last 40 years alot go lost due to ignorance and the rural exodus.