Not too sure on the first question, I don’t think it would make a difference as the 17′ only affects the diameter of the tire, with a smaller size (ex. 15″) you’d have a bigger sidewall on the tire which I don’t think makes any difference in traction. Personally I stick to the size recommended by the manufacturer which can be found on a sticker on the inside of the drivers door, if you can’t find the sticker check your owners manual it should say where it is.
Some good cheaper tires I’ve had good luck with myself are Hankook and Nexen.
-Kugan