This is... not Great.
The renders are fine, from a quality standpoint. But the backplate implementation is less than stellar.
The perspective seems off on the "top-down" shot.
The car is way too small for most of the shots. You used hdr/backplate from hdri-locations? if that's the case, the backplates are from the danish country side, pretty narrow roads, hardly room for two cars of average width.
Did you check that your horizon line in the render matched the background?
The B&W renders don't really work, most of the values seems to blend together. You have far better seperation of motif and background in the colored versions.
Most of the backplates have some natural lens blur which you omitted from the 3d render.
I like the the first shot on the behance page, but the car is too small.
