I would agree with that last statement, we were there in our 28 ft class A without TOAD 2 years ago, and the northern loop was a lot more stressful to drive than the southern loop. As to driving any class A, the issue I had was the relatively narrow roads and all the Cruise America rental RV's with drivers that did not know where their side of the double yellow line was.
So can it be done, yes, but don't expect many parking options at the tourist sites, and don't expect it to be a low stress drive.
2002 Safari Trek 2830 on P32 Chassis with 8.1L w/ 400 watts solar
2017 Jeep Cherokee Overland TOAD with Even Brake,
Demco Commander tow bar and Blue Ox base plate