Fishkeeper1, sunfish in general do best with a diet that closely resembles their natural diet, such as insects, crayfish, smaller fish, and so on. This is a higher protein diet, but small amounts of vegetation will benefit your fish as well. You'll find a good balance in a quality cichlid pellet food. If you prefer frozen or live, it's best to offer a good variety of everything, but emphasizing more on the protein.
Greens, like all sunfish (including hybrids) look best around their breeding times. They won't be as colorful as they are during these times no matter what you feed them. Also, given a good diet, good feeding regimen, and proper tank space, you should see them reach their maximum size within a few years, which is healthy. Powerfeeding to hurry this process creates unhealthy fish.
There isn't a whole lot of knowledge on the temperament of the hybrids of these fish, but from what I've experienced they aren't any more aggressive than greens or pumpkinseeds. It also depends on the particular fish, I think. I've had plenty of pumpkinseeds that give greens the shaft, when it's normally greens the rule tanks.
Hope this helps.