I took 14A on my trip last year. One of the best roads of that journey.If you want to take a slightly different route on the way west take 90 vs 94 and then in Sheridan WY take 14 or 14A (I did 14) across the bighorn mountain pass and into Yellowstone NP. That stretch of road was one of the most memorable stretches of road I've ever experienced in the entirety of the USA that I've travelled.
Indeed, I had to go back-and-forth between which one to take and opted for 14 as there was a big pull-off spot I could see on Google satellite where I could spend the night if need be - it was a bit late in the day when we started the trek.I took 14A on my trip last year. One of the best roads of that journey.
You really need to consider riding in the Kootenays. Some of the best roads in B.C. are centred around New Denver (Hwy 6)... just to the west of your intended route.