Outside the Max phase of a Max Battle, Pokémon use their usual fast and charged attacks. It is usually desirable to use a single turn fast attack, as each attack landed charges the Max Meter. The list is sorted to minimize turns, then to maximize bulk. Type effectiveness of the boss's attacks are just as important a consideration as bulk. The effectiveness of your fast attacks is of less consequence. Charged attacks are not typically worthwhile in Max Battles, though this is by no means always the case.