The Forza franchise is split into too distinct subgenres.

Forza Motorsport is the realistic simulator. Tire temperatures affecting grip levels of simulation.

Forza Horizon is the arcade racer. It uses Motorsport as a basis for its basic driving physics, but values are tuned or ignored to maximize the arcade factor of driving.

Horizons driving model kinda feels like Need for Speed, games by Criterion, but less mobile oriented. Its also a little similar to Test Drive Unlimited 2, but the grip is a little lowered to make drifting easier in Forza Horizon.

Its not like Mario Kart, Blur, Split Second, or Asphault. You could maybe try a demo to see if you like it, but you will probably have fun with it.