Machop seems to be entirely random, with an equal chance of using any of it's 4 moves.

Makuhita will favour knock off if you have an item, but it will be strongly discouraged (possibly impossible) if you do not have an item, even if it will kill.

Makuhita will only use Arm Thrust if the 1st hit will kill.

Brawly will not use a Super Potion if he can 100% kill that turn.

The safest way to beat Brawly (almost impossible to die) is to remove the silk scarf and spam echoed voice (no x special), this also is unlikely to result in him using a Super Potion)