Most cichlids are very aggressive and would probably end up killing your Platys. Research the type of cichlid specifically you want to get and see how aggressive they are first, there are a lot of different kinds of cichlids
It is not a good idea to have them in one fish tank. The cichlids are very aggressive fish and placing them in a tank with other less aggressive fish is not a good idea. You can inquire from the fish store about the best companions to your fish.