The ultimate downshifting IS heel and toe, no question about it. But you can be fast without it. It depends on how much power the car has and how hard the clutch is. If you have a 400bhp car and a unsprung puck clutch you HAVE to heel and toe. Not only will you ruin the balance at corner entry, you will also destroy the driveline, especially the cluch will overheat and wear extremly fast. I cant heel and toe yet but i HAVE to learn it. When i AutoX and track my car irl (Rx-7) the rear is all over the place when downshifting. But as i said, if you have 120bhp and a stock or realtivly weak clutch its no problem.