I was thinking of games like Starcraft where even flying units had to stop before firing, as opposed to Total Annihilation where most (all?) units could fire on

I was thinking of games like Starcraft where even flying units had to stop before firing, as opposed to Total Annihilation where most (all?) units could fire on the move. So I guess I'm concerned about the ability of units to do multiple things at once, which os something every game should have.