You'd likely be able to tell they're hybrids (or if not, post pics of them and get some feedback) once they get some size on them (1.5-2" maybe). Sometimes its hard to tell though, which is why its safer to just not keep them off the bat if you're not positive of who mommy and daddy is. Just my opinion
Sexing them as juveniles is difficult. With the fish you have, male auratus change colour as they mature, females stay yellow. You know obviously that one is a female, but unless you saw them actually spawning, you can't be sure of the other yet. Kenyi are the same way...females stay blue, males change to a goldy yellow as they mature. Red Zebras are hard to sex to an untrained eye, but typically males will have a blue tint to them (unless of course they're the natural blue males, then its obvious
) Other mbuna are very difficult - like the labs. They're basically impossible to sex visually unless you see a female holding or a male spawning.
All-male mbuna tanks are an incredibly bad idea. Even an all-female tank may not work with the aggressive species you have in there. For the harmony of the tank, its really best to have a 1male, 3 female ratio typically for most mbuna species...any babies they produce often get eaten if left in the tank anyway, very few will actually survive long.