Pitch shifting is super easy to implement, lightweight, and it sounds very well when done correctly. I see you improved it a lot already, well done! I love it :) With enough samples and good transitions of pitch/volume you can go really deep as you can see.
About the game speed it is a tough question. It really depends on the feel you want to give to your game. As long as it's consistent it should be fine. It also depends if you want to make the game for casual players (probably more audience) or if you want to make it more of a simulation (less audience, but is it really about the numbers?).
Maybe a good "in between" would be to just make two vehicules, one that has to play more with the drifts but is faster, and the other that is easier to control but has a lower max speed. In that way you can play with both styles and the game is still balanced. It's nothing new, kind of unoriginal, but that's also because it just works.