From Coeur d'Alene to Placid Lake (near Seeley)

You could even pick up ID200 at Sand Point. It follows a straight river valley all the way to the US93 junction. Other than the Sandpoint area it isn't a major tourist/rv route, with the associated businesses. But it's an easy drive.

We just drove part of that route, on MT-200 from MT-141 to MT-83 (enroute to Glacier NP). That section of MT-200 was a GREAT road, scenic, good condition, and low traffic. In fact, we decided we're going back to camp along the Blackfoot River. What a great area of the country.

200 is a great road, wide enough, pavement good, etc. We were just there (including at Placid Lake) a couple weeks ago. 83 from 200 to Placid Lake is smaller, winding, some traffic (I think it's one of the main ways to reach Glacier NP). Still ok for RVs though, just take your time (and ignore the steam coming from following drivers' ears...) :)