Jack Demseys and Green Terrors are generally known to be .... well.... terrors! There are some community cichlids but some of the larger ones don't really belong. Firemouths are great community fish as long as they aren't breeding. Mine is such a wuss that my gold gourami chases it! I think firemouths are central american but I usually group them in with south americans. Severums are good community fish they get to be about 10 inchs but usually aren't too aggressive.
In any cichlid tank the number of fish is going to be low. They are all territorial and some get to be large. Firemouths get to be 6 inchs and severums get to be 10". I wouldn't suggest more then a few pairs of fish.