Sometimes I drift, sometimes I don't drift. It would depend how the car is set up. For example, I-B test 8 can be drifted beautifully.
I usually copy whatever the demo car does. If the demo car drifts, I drift. If it doesn't drift, I don't drift. I find I am faster than it about half of the time. I've only had the game for 1 day, and I have 34 golds, need 6 more before I go onto Special, which I imagine will be a lot harder and take a lot more time.
In terms of driving style, I tend to favour the 'shortest route' way of doing things, rather than the 'straightest turn' philosophy where you use all the track.
Is the demo car a person driving, or an AI? It seems a bit smooth for a human driver, but it does sometimes make mistakes. For example, in I-A test 6 (the one in Rome, in the Zonda C12), the demo car is too conservative in the first corner, and turns in way too late for the second corner. I gained about a tenth of a second if not more on the demo car, simply by turning in early, tapping the brakes to help turn the car, and getting exactly the same exit speed.