Yes triggers are predator and fierce carnivore...... They eat almost everything given.... As for compatibilty wise, it depend on what trigger you get, for example niger trigger or queen trigger, they are rather docile therefore you might be able to mix them with other triggers....... But some other trigger remain fierce and will almost kill any fish added and one example is undulate trigger............ And mixing with other trigger also depend how big is the tank....
Anyway trigger queen is a trigger expert and have successfully mix some triggers together, do ask her about it