Right now, if you get into a 500hp car, will you be able to drift it? No. If you got into a bone stock ka 240, would you be able to drift it? No! Learn first on a stock car, and then when you feel secure with that begin to upgrade. If you are focused on drifting, suspension first. You can very well ry to start out with a higher horspower car, but even though i can't speak of much experience, i will guarantee it will be harder to learn on a fast turbo car than a ka24. To answer your one question, can a drift car be fast, I'd have to say yes. Look at the pros in japan, there are a number of them drifting cars with 500+ hp, and i guarantee that they're pretty fucking fast.
Also, look at old threads and search stuff, you'll find that nearly everythign has been discussed already.