There is a short stretch with zero shoulders and heavy traffic.
It would be nice if Blankenship were paved all the way or shoulders were available on US 2 -
But such is not the real world in which we live.
About camping in Glacier - -
Apgar and St. Mary are like zoos with a zillion RVs.
I think one or both also tack on a "reservation" fee for hiker biker camping.
On the west side, either Sprague Creek - close to MacDonald Lodge or Avalanche - close to the Avalanche Lake rail are nice.
On the east side, Rising Sun is super - with showers available and trails and the lake just across the road.
You are not planning to go to Many Glacier - the finest road access in the park?
Lord have mercy, child! I do not know what's gotten into you.
Again, hiker/biker campsites - camp store and pizza café nearby - plus Many Glacier Lodge.
Highway 49 is steep and pretty narrow - plus US 89 has a big climb out of St. Mary but with two lanes uphill.
After that US 89 is also narrow with a good deal of summer traffic.
Still, Two Medicine is certainly worth visiting - great hikes, camp store.