As long as you are going to Mt. Washington, consider the Kancamagus Highway in the White Mountains. There are innumerable scenic spots along the way, and you should be able to manage parking with your motorhome. Lake Winnipesauskee is very scenic, and there are lots of small towns around it that aren't congested.
TT: 2019 Minnie Winnie 2500FL, e2 WDH; former 2015 Keystone Bullet Premier 19FBPR
TV: 2012 Ford F-250 Lariat Super Duty Crew Cab (gas 6.2 L, 3.73 gear ratio 2WD, 172" WB)