RE: Your planned Alaska trip.....the trip is not what it was years ago and you shouldn't listen to horror stories repeated and embellished over the years.
Yes, you'll encounter some areas of construction - just as you do in the lower 48. You will encounter some sections of frost heaves which are usually well-marked. You soon learn how to spot these areas from a distance. Otherwise, it a good paved route all the way.
RVs of all sizes make the trip and you'll see many 40+ rigs on the road. We did it in ours and had absolutely no damage or problems. The key is to drive slower than you may normally. The trip shouldn't be hurried.
It's not always sunny and when it rains it could last for days. A bigger RV makes it a lot more comfortable.
The RV parks are pretty much basic gravel parking lots and any size RV will fit. We used public parks and boondocked in awesome areas with our 40' MH.
Don't worry about size. Maintain your RV. The most important thing is to have good tires on it. We replaced all of our 6-year old ones just before heading up. We did so in Oregon - no state tax. :)
Follow the Alaska/Canada forum on this site and it will give you lots of good information.