That is kind of a trick question. Wings are used for purposes. Down force and or smoothing air as it passes the body. The down force you get from a wing depends on area, angle and shape. You don't want more down force than what you need. It would be like picking springs/ shocks the wrong rate. Generally the down side of down force is drag. A wing can knock off a lot of MPH, but if your getting tire shake or instability you need just enough to stop it.
Frontal area is drag. The more angle the more frontal area. A wicker bill even an inch high can add 3 or 4 inches of unseen frontal area.
How the air that exits the rear can be very disruptive to handling. Every one has heard why turds are tapered, so your butt don't slam shut. That is why air should leave the rear of you car smooth. The slamming of air, buffeting, will give you bad handling. Everyone has been behind a semi on a windy day knows this feeling. It's the tail wagging the dog.
Every car needs different that is why funny cars have big scoops for down force and pro stocks have about straight just to aid buffeting and a little down force. The lower powered dragsters don't need the wing a AA/FD does.
Most bodied cars use their body and a spoiler as a wing, by limiting air going under car it creates low pressure. The curve of the roof promotes high pressure and the spoiler transitions air at exit.