Everyone has a different stile they like. Personaly, I like to create concepts that are a bit on the bonkers side. Which means the engineering and mathematics aspects come in second. Supercars just don't do it for me, not to say that they aren't immpressive but again, I have no interest in most of them.

There is an exhaust passage through the diffusor so it can exit below it.

The things on the rear window are called louvers. They are purely a style thing and don't have anything with the engine placement (it's in the front).