think about this....if the plane is blurred and the background is still, you will show motion, or,....you can have the plane blurred and the background sharp, you can still show an effect of motion, but with both blurred, its a bit harder to see motion unless you are panning with a very slow shutterspeed ..........
........I have done lots of photography and understand the principles needed, to show the perspective you intend to display..........

Here is the first without any edit, then the two different ways to show motion.........