3x what 2Gypsies said. We went with our 40' MH with 4 slides and towing twice and never had an issue. Personally I have seen worse roads in California.
One trick that worked for us,is if someone wants to pass you on the road we did not pull over. This would cause them to throw rocks at you. When it is safe we would slow in the road and turn on our blinker for them so they knew it was safe then they could go around. This worked because it would make them slow down before passing.
We never really had traffic, the travels are pretty easy and usually you meet up with most of the people in camp that day.
Again what others have said the Milepost is great. We always have ours with us when going to Alaska.
As for direction, We travel up the 15 and cross at Sweet Grass, through Calgary to Edmonton area over to the Alaska Hwy. Then return down Cassiar hwy to Jasper, Lake Louise and Banff, before heading back down to Glacier and the 15 to home in Bullhead City, AZ. This is the route we are doing again this next year. This time my sister and Brother-in-law are following in their MH.
Check out the sticky at the front of this forum for more ideas of what to see and do. I had great help from everyone on this forum putting that list together.