Most of the time yes you will have less issues as you mention with stock from a good breeder.
The size difference as others have said is because they breed or early lay, that's it. That's also why the type is not to SOP on birds because they breed for early eggs production and lots of it regardless of what breed it is. Since they replace their flock every year long term health or long term production is not important. Small size doesn't matter because they're not butchering extras for meat.
I would still encourage you to seek out a breeder who does breed to the Standard even if you don't have any interest in show, the reason being that the standard is not written for aesthetic reasons. Form follows function and the standard is written for each breed to best meet its original purpose, be it eggs, meat, dual purpose with more emphasis on one or the other etc etc.
As far as breed recommendations for the NW, unless you're in the high mountains most breeds do really well here. I feel the ultimate home flock fowl is the Langshan. A very old, very hearty healthy breed. They are excellent layers, and the cockerels get to good size for eating. They may be hard to locate locally though (until next year at least). There are some excellent breeders of Jersey Giants, Australorps, Rhode Island Reds, Wyandottes out here and those would all be good fowl for dual purpose fowl.