I have a 27 Seasport and fish pretty much all year round. The boat has never been winterized. I fish the North Sound from November to April as seasons allow. I then fish either the West Coast of Vancouver Island or off the Washington coast from May until late August. Then I fish either the Columbia or Oregon coast until the end of October.
As for boats, I would strongly recommend that you stay at the top end of size range 18 to 22'. The coastal waters can flare up very quickly when your offshore and even fishing inshore. I have found that I prefer an enclosed cabin since much of my time is spent out there when the weather is cold and wet. It's nice to step in out of it once in a while. This is especially important if you plan to spend the night in your boat. When we go fishing we just drop anchor or pull up to a float and sleep in the boat. I would also recommend sterndrive vs outboard as it gives you the option for cabin defrost and heating and more battery charging capability if needed.
As for make of boat, I would recommend Seasport, Osprey, Almar or Glasply. You won't find a lot of these on the used boat market as they are quality boats and usually sell quickly when advertized, but they are available.