We have traveled the Alaska Highway twice. The first trip was in our ERA class B in 2012, and confirmed the idea of traveling farther afield that led to our moving on to Scout our Tiger RV unfortunately we were not blogging at the time.
The second trip was in 2017 in Scout and the blog entries are below. Anyone who is interested in this trip I would highly recommend it. The main Alaska Highway is paved the entire way and the road quality is generally good. There are towns and services spaced along the way so you need no modifications or extra fuel to make the trip as long as you follow the 1/2 rule. If your tank is at 1/2 you fill up at the next gas station you see.
In Alaska the main roads are also paved and generally good quality. Any class B or C RV can handle the main roads on the trip, and we saw plenty of class A and large travel trailers on the highway.
Some of the side trips involve gravel roads, but again in general they are well maintained and 2wd will suffice. If the conditions have deteriorated the highway departments are good posting road conditions. The two roads to the Arctic Ocean involve hundreds of miles of gravel, but we saw all kinds of vehicles on these roads including cars, semi-trucks and 2wd pickups, though I think some discretion is required.
The sights on this trip are fantastic and make the effort more than worth it. There is everything from majestic mountains, to Fjords, to Tundra. The wildlife is plentiful and I can almost guarantee you will see interesting animals frequently.
We cannot recommend this trip enough.