Is it logical that I could / would mostly camp but stay in a hotel every 5 day'ish?
Doable on the Northern Tier, at least through Montana. Plenty of camping opportunities. Motels in and around Winthrop/Twisp, WA. (You may want one after crossing the Cascades.
), Tonasket, Republic, Colville and Ione, WA,, Sandpoint, ID, Libby, Eureka and Whitefish/Columbia Falls, MT. From Cut Bank, MT east there are several towns with motels (e.g., Havre).
I highly recommend the Northern Tier section into Alberta, Canada. Waterton Village, about 5 miles off route, is a nice place for a day off. There is a great towne campsite along the lake with mountain views and a boat ride/hike combo you can take.
When are you planning on starting? Glacier has gotten a good amount of snow this year. If that keeps up, Logan Pass might open later than earlier. The Northern Tier was my first ever tour, so I have a soft spot for it. You don't want to miss Logan pass. Yes. Central and eastern Montana can get monotonous, but I still enjoyed the area and the towns we stayed in. Harlem allowed camping the city park and had a nice public pool. And if you get a killer tailwind you can knock off some serious miles with relative ease. One day, during a 20 mile stretch into Malta after breakfast, I sustained 32.5 mph for several miles. When I finally went into the red for too long I had to dial it back to 28.5 mph.