Not necessarily. Unless you got them from a very reputable breeder who bothered enough to keep his lines clean or bought them somewhere, reliably ID'd as wildcaught or F1, you're buying hybrids.
I don't know. When it comes to mbuna there are just way too many flavors. Right now I absolutely love the Zebra Chilumbas. Before them I was all hot about P. sp. Flameback and before them it was all about Cyno. sp. Lion "Mara Point". But then again it's hard to get over the old favorites like a really good line of brilliant red zebras or big gorgeous M. greshakei.
Right now if I could only pick just one type of mbuna to breed (you said type, not species

) it would be Petrotilapia. The bigger the better.

If I had to go with just one species...I'd probably go back to Labeo. fuelleborni. They're like big beautiful honking nosed puppy-dogs. lol