I have played with experts and here is what they were doing:

• forget Kong or Bowser, they can’t accelerate, and if you’re hit, you’re dead
• get one fast enough with a decent acceleration
• ALWAYS DRIFT ALL THE TIME, it takes time to learn but that’s what pros do
• don’t take shortcuts, they are actually longer than the regular road, and even with the boosts on the road, you can’t drift properly

Drifting seems to be secret.