In my opinion, if I had to make "character classes" out of the main five, Cera would be the DPS/heavy hitter, Ducky would be hard to hit and mobility-focused (with additional swimming bonuses if the system has water mechanics), Petrie would be weak and fragile but able to fly, Spike would be a slow but high-HP tank, and Littlefoot would be an all-rounder with some sort of morale/leadership playstyle for buffing the other characters.