The non-cosmetic physical difference between P3+ and P3- are details such as performance braking, suspension settings, wheels and tyres. The performance of the high spec 'binned' motors and higher powered inverter of the P3- is toned down in software by removing track mode and reducing the maximum speed to better match the brakes and suspension but the stunning acceleration is the same as for the P3+.
No, our P3D- has track mode. And if you have the Tesla service center install an OEM spoiler, the maximum speed is unlocked too (we did that - now shows the little spoiler on the vehicle graphic representing the car). Apparently top speed is related to the back end needing to be kept level rather than the brakes and suspension.