So, I'm using a keyboard and mouse to play Rocket Racing and I know it's not as good and that I can't compete with people using a controller but I think a Keyboard and mouse category could reward my work.

Yes, it is easier on controller, but there isn’t any advantage by using it versus controller to warrant a category split. There are plenty of top level runners that play K&M

Normally racing games favour controller but I think this game is actually superior on mouse & keyboard, there's something about binary steering inputs that seem to be better for getting the most optimal drifts. A fully optimised M&K run is unbeatable on a controller on this game. The best times on this game have been done on either M&K or someone using a controller but also a 3rd party program to output as M&K. Sure a controller is easier to use but the ceiling isn't as high.

I even tested it myself, I use both, depending on the game but all my runs on this game have been done using controller inputs, although I went on Day Drifting at one point just to see and managed to beat my own controller pb using M&K after a couple of hours and that's not even close to enough time to be fully used to it yet

I agree that the two inputs are pretty comparable in their ability to perform at the top level. KBM may even have a slight edge.