some cars are pretty hard to drift stock... lotus espirit, for example =p so not all cars are as easily drifted.
4WD's, I don't think, can be drifted stock. I tried really hard using a 4WD Celica GT-FOUR with my normal basic mods (~300 HP, minor drive train mods, sims) and I could not get it sideways at all. I had to tinker a bit with the LSD before I could get it somewhat close to sideways action. I never did finish it.
If you're just getting into drifting, I'd recommend light drivetrain mods like the Carbon Drive Shaft, Double Plate Clutch, and Sports Flywheel. Weight Reduction helps too, I usually just go up to level 2. These mods don't make you overly reliant on power but they make the car more responsive and less error-prone.