With self drilling screw should I use a drill or a driver?
No matter what drill or tool you use to set a self tapping screw, take it easy. Turn the screw at a moderate to slow speed through the entire process. Once the self tap "drills" through the metal the screw then begins to screw in. After only a few revolutions the screw will be set. If you are really spinning  the screw you can easily strip out the hole.