I'm a huge CJ fan. I've watched him run every yard of his NFL carrier. I've watched him live in college and in the NFL multiple times. He is as fast as there has ever been in the NFL. He has legit football speed and legit track speed.
I'm also a track coach. I have never coached anyone as fast as Bolt (obviously), but I know what it takes to be sub 10 fast. I know what speed is over that distance
That being said, Bolt would beat CJ in a straight up 40 yard sprint, but it would be somewhat close. The 40 is 90% power and explosion. Come 100 meters, where top end speed, stride, and form come into play, the gap would be so big you could park a bus in it.
As a Titans fan, CJ runs his mouth about everything. This does not surprise me.