You have plenty of control. You control the order of upgrade priority. Even which tracks to race in. Would you prioritize acceleration over top speed? Long tracks and short tracks need different approach. Should you save to get big upgrades but risk losing early races, or spend all out for quick wins but lower, slower reward mulitiplier? Tracks evolve, AI opponents evolve, so should your approach. Won't be so fun if you always win easily in an idle/incremental. The point is finding a good balance, hence season wins are awarded based on racers' average finish positions and not by point system.
I guarantee you though, all your level ups matter, but keep in mind, the AI opponents level up too.