You said you were going with the GTYR weighted flywheel,correct?
I would suggest trying that modification first,the extra weight on the flywheel should help smooth out the low end power delivery of your 450.
Then if that is not enough then try the WR cam.
That's a great plan, the flywheel should make the engine more luggable at low rpms. Adding a couple of teeth to the rear sprocket should help too, I know it helped my yz to behave better at low speeds. Killing the low/mid power on a yz is just pure heresy, blasphemy.