if you go with a drift boat you have 3 options
fiberglass-warm in cold weather and quiet over riffles but they dont track well when pulling plugs
aluminum/metal-cold as hell in winter and quite a bit louder over the riffles but track extremely well whenn pulling plugs
wood-warm in winter,quiet on riffles, and usually track and stay true with plugs...but being wood if you beat on them you WILL hurt them..which can be bad.. :p
then there are sleds..if you want something to go anywhere buy a 16-18 foot sled or john boat with a semi-vee hull(works better in the bay or rough water) and in my respects get on with a tiller control,they are just easier..put a 70 to 90 hp motor on it and skip it across the water
as to your question about where to fish..classic rivers around here(western washington) you got the satsop,whynooche,humptulips,and chehalis..just try to learn these first.
down south, more towards you there is the cowlitz,kalama and most of the larger columbia tribs. those are some of the basics for south-western wash. sorry but i dont know anything about oregon.
just like anywhere else though...look at a map..find river...ask around about it, look and fish and wildlife's catch records for it and then go stooge around in it..
good luck and welcome to the board