In tour races, the higher the cc you select, the better your opponents will be. You can change the cc by following the below steps.
1. Choose a cup/course.
2. Choose a driver, kart, and glider.
3. On the "Ready to race!" screen, tap the cc icon.
4. On the Choose a Speed screen, tap the cc you want to race at.
5. Tap OK!
Note: If you can't change your cc, try increasing your player level first.