Okay, time to fill in the people that haven't played GBA ToP!
By default you play semi-auto mode, where combat plays in...well, semi-auto. Pressing an attack button would make the character run up to the mob and attack it and when finished, run back. Which got really annoying, and unfortunately you couldn't switch to manual until halfway through the game or something through an item.
Manual gets rid of what semi-auto does, and lets you play how all Tales games play now.
Combo mode has you inputting commands ala fighting games to do artes. 236A, QCF A, whatever notation you want, would do an arte.
Now in the first place, virtual touchpad controls suck dick. I would rather use the 360's default DPAD, that's how shit it is. When you combine an action game or anything that requires precise inputs with virtual touchpad controls, you're asking for trouble. When you're putting fighting game controls on virtual touchpads, why bother playing?