I'll be doing my third loop tour from/to Missoula, MT starting on June 14. Ten days of riding with the opportunity for a rest day or breaking one day into two shorter days. All camping except for one night in a motel in Butte, but even there you can camp if you don't mind a KOA near I-90. Some relatively short days. Some long days. (IIRC, the longest day is 80 miles but with little elevation gain.) Thing is, there are some mountains. There is also some dirt riding. Most of the dirt is benign, and there are workarounds for all of it. However, there is one 20 miles stretch that has some climbing and descending and washboards in places. The only workaround for that stretch adds some noticeable miles. Eliminating another 30 mile (but slightly down hill) stretch diminishes the beauty of the route.
Logistically, Missoula is an easy place to start a tour for me. I can fly to MSO from the east coast and take a short taxi ride to the pretty quiet KOA on the west end of town. I ship my bike to REI, which is a two block walk from the KOA, and it's ready to ride when I arrive. REI holds my bike box and duffle bag and I pick up fuel for the stove and any last minute items I may need. The next morning I shove off. When I finish, I drop the bike off at REI, give them the shipping documents, pick up my duffel bag and go have a beer.
In terms of meeting people, the first two days and some of day three follow the popular Trans Am route. After a detour off that route you rejoin it at Twin Bridges and take it for another day to Ennis before leaving it for good. From there, you end up on the L&C for a bit. Last time I rode out that way I encountered at least a dozen people doing the Trans Am or L&C and I didn't do the mileage to Ennis that year. This year my penultimate night on the road will be spent in a town where ACA's Cycle Montana supported tour will be staying.
Send me a PM if would like details, including a route map with elevation profile.