[Big time]

Let's suppose you are designing an streamlined car from scratch.
The car has a wide track and a narrow cabin.

What is more aerodynamic:
A car with bulging fenders or fender flares.
i.e. to cover the width difference between the wide wheel outer edges and the narrow body for example measured at the doors.

Or a car with a wider body. Where its body width (measured at the doors) is as wide as the wheel outer edges?