1. The Coolhead is a good product and will move your powerband down lower, basically the power comes on sooner. A properly milled head does exactly the same thing, only a lot cheaper. You can change out the domes on a Coolhead down the road if you want to, but most people never do. Either way it is about a +2.5 HP mod. Coolhead $250, milled head $35.
2. To adjust the timing you can either modify your stock timing plate, or buy an adjustable plate. I would stay away from degree keys if I were you, many people have had problems with them. Not everybody, but enough to warrant concern. This mod is good for +2.1 HP at +4 degees advance.
3. I don't have an opinion on the tires.............