As you note, "accepted practice" != legal
It's definitely illegal to pass stopped traffic on the left, if you cross a solid yellow line - you're just illegally overtaking. I think this is still illegal even there's
just about enough room to squeeze past them and stay in the same lane as them and to the right of the yellow line - you're "sharing the lane", but whether that's legal or not? Whether you'll get busted for passing on the left or not is another matter.
The same goes for passing on the shoulder - it's always illegal, but you're probably not going to get busted.
My experience (yay - anecdata!) has been that unless there is a cop parked on the shoulder, you're probably fine passing on the shoulder. Also IME, cagers react much worse if the see you passing on the shoulder, but if you're quick, it's not a problem. They're kinda used to bikes overtaking them on the left, illegally or not. But using the shoulder seems like cheating. I've had passengers open their door very slightly to scare me. YMMV, obviously.
And Hwy 299 is fantastic - better than Hwy 36 IMO. And Weaverville holds special memories for me