Being your in Seattle I'd be inclined to keep the hard top for the winter rain season, and use your soft top during the summer rain season
Personally you'll be better off with smaller wheels and larger tires in the long run as the tire costs for 18s is pretty high compared with the tire costs for 17s or 15s I've found. But if you insist 20s - well no comment. Many here go with 17s and a 33" tire like the duratrac with good results and you won't need a 3" lift, if you want 35" then you'll need that larger lift.
I do agree, get some miles on it and make sure all it working right before you go spending a lot of money. Since I bought mine used I'm waiting till my warranty is up, and I've got the money saved to do the lift and wheels/tires right and at the same time.