Pikachu's final smash is very strange, as it is called volt tackle, yet he just turns into a big ball of electricity and flies around. To actually represent volt tackle, I believe Pikachu's side special should be changed from skull bash. Instead, Pikachu can charge volt tackle with side-b and his signature "Pika-pika-pika-pika" then, when you let go, "PIKA!" and Pikachu begins running across the stage at full speed. You can cancel this by attacking or jumping. In the air, this move would have no effect. And yes, if you do not cancel out of this attack in time, you will go running straight off the stage.