You can mix Mbuna's with Haps and Peacocks. You just have to research their temperaments. My 125 gallon tank has a few of each. I've had to rehome a few fish because they were too aggressive. It's trial and error sometimes.
I went to my LFS
and saw a blood parrot and flametail (both adults) in the same tank. They were swimming side by side, apparently owner had his tank break so had the store holding his fish till he could set up a new one. The 2 fish were best of buds. Was really weird to watch.