We just returned a week ago, and from Canada came down that route - Bangor to New Hampshire and Vermont via highway 2. We drive a small class C and were not towing but saw plenty who were. It's not a bad road, just a little slow due to passing through small towns.
Didn't have a lot of time, but just hit a few highlights. There's obviously a summer's worth of things to do in that area. There are hiking trails, rivers and lakes virtually everywhere.
We stayed in Tarry-ho RV park by a river in Twin Mountain, NH three nights. Nice friendly folks, great internet, no laundry facilities though. Ideal location to take the cogwheel railway up Mount Washington, which we enjoyed a lot. Saw plenty of hikers, either round trip or riding one-way and hiking the other. Bring warm clothes if you go up there.
Had lunch at the beautiful, historic Mt. Washington hotel near there in Bretton Woods. The next day we drove the Kanc highway to Franconia, but it was too foggy to see much. The state park and national forest have plenty of hiking trails. Enjoyed lunch at the funky Cabin Fever restaurant in the town of Bartlett.
Then headed to Vermont on 2, stopped at the Cabot Cheese Factory (interesting tour, cheese tasting) and Ben & Jerry's (packed, but kind of fun.) Down to the Woodstock Quechee area.
We stayed there at the Quechee KOA two nights and would highly recommend it. (I'm no KOA cheerleader but this was probably the best I've been to - great location, property, and customer service.)
While there, we drove on highway 4 through Woodstock to Plymouth to visit the Calvin Coolidge historical site, went up a gravel road to Sugarbush Farms to taste and buy maple syrup (lovely family farm, very simple, welcoming, and not highly commercialized.) Walked above the Quechee Gorge, took photos of the covered bridge, and stopped into the Simon Pierce glass and pottery shop/restaurant in the old mill.
From there we headed home. Would like to go back to Vermont and spend more time.
I posted reviews of the campgrounds on RV Park Reviews.com.