It all depends how the track is made. There are some really fast tracks that have sharp enough turns that they require drifting. There are other maps that are built to be completely fullspeed noslide.
Personally I prefer some drifting mixed in there, cause its just so much fun. But the car is also very adept at nosliding at incredible speeds, especially on the platform blocks.
The drifting is fun because most times it's also possible to do full throttle, but you just tap the brake to initiate your drift to take the turn a bit tighter... but you're still rocketing through the turns. I rarely let off gas on any map unless its a VERY techy map.
I have my brake assigned to a secondary key on the left side of the keyboard to make it easier to control when I'm doing a drift.
Offroad, you will always slide. It's offroad.
GP... pretty much made for drifting, but with the right lines, a lot of tracks (even tech ones) can be taken noslide through some parts if you get your line right.
The only parts that will probably be unfamiliar to you if you're used to TMNF, is the physics of the car when driving loops, inversions, and wallrides. The car literally sticks to the surface of the wall, and this causes some strange things to happen. It's a lot to get used to, but a lot of new and cool things become possible with it.
I hope I answered your original question.