If the dog is a breed with naturally shortish hair, it is easy to tell “play aggression” from “real aggression”. If the hair on the back isn’t up, it is all fun and games…disregard all the snarling, growling, and barking. Also, if one dog yelps, the other will back off when playing, but not if it is a real fight.
IME dogs that regularly roughouse with other dogs have excellent social skills, and are very unlikely to start genuine aggression, or escalate a nervous nip into a furball.
Also, for some reason dominant dogs will usually let the youger underdogs “steal” toys from the. Food, however, is a whole different kettle of fish.