I do not understand this well. Is this sarcasm or I didn't really get how Religious Convert worked?
If I understand the Religious Convert ability well, Kongo need to have a majority religion to enjoy all the beliefs. Currently, all players may enjoy all the beliefs except the Founder Belief. For the Kongolese civilization, they enjoy the Founder belief but not the Worship belief (no Holy Site) nor some of the Follower beliefs (if it's: Choral Music, Feed the Word, Religious Community, or Warrior Monks).
Having +300 Faith with religion, I suppose it means that an AI found a religion, found it can expand the religion and add a Founder belief, choose the "Pilgrimage" as a Founder belief, convert at least one of your city (and then you spread to yourself: helping this civilization to win a religious victory), make sure that more than half your cities follow that religion to enjoy the Founder belief, and then make sure that 150 foreign cities follow the same religion.
I don't find this overpowered. It just mean you are stronger when a civilization is about to win a religion victory. But, I may do not understand this ability well. Explanation? (or I am very bad at detecting sarcasm?).