They share a slot and start as Charcadet, which evolves into either of them at level 4. Armarouge is tankier and more ranged, while Ceruledge is faster and more up close and personal.
They all the Flash Fire Ability, which allows them to tank 10% less from incoming ranged/AOE damage and get a slight power boost to their attacks for 10s.
Move 1: Ember
Shoots a small fireball forward, inflicting a burn.
Move 2: Flame Charge
Cloaks itself in flames (which have hitbox), Charcadet blazes forward.
Armarouge Move 1 (lvl 4, from Flame Charge):
Armor Cannon: At the cost of 50% of its Defense, Armarouge stands in place and charges a fireball, which it then fires forward.
+Upgrade: Armarouge is now unstoppable when charging.
Armarouge Move 2(lvl 8, from Ember);
Expanding Force: Shoots a small psychic projectile forward, which then expands into an AOE move that has a suction effect and does damage.
+Upgrade: Bigger sweetspot (which is the center)
Unite Move: Mega Arma-Cannon
See Samus' Zero Laser.
Cerulegde Move 1(lvl 4, from Ember)
Shadow Sneak. Basically Sableye's but with more range.
Ceruledge Move 2(lvl 8, from Flame Charge):
Bitter Blade: Charges forward and slashes the foe, dealing damage and siphoning half of the damage.
Unite Move: Cerulean Killing Edge
Ceruledge does Marth/Lucina's Final Smash.