1) Well, I can't say which is better... Each class is good. Warrior usually utilizes buffs + phantom spell to help his troops. The Mage can become a real nuker by the end of the game. The Paladin is jack of all trades, master of none. However, he can be the hero that resurrects a completely obliterated stack with Resurrection lvl 3 skill.
2) Now that I don't know. I never used that cheat even once in the 9 months I've been playing the game
