365 and 8 and 9N are all decent roads--not glass smooth, of course, but not by any means what I would consider rough. 17 is generally fine in terms of not having particularly rough pavement etc. as well, even through the Appalachian Gap; while the road may be a bit rough, it matters a good bit less when you're going 20 mph or so instead of 50...and towards the top of the gap, that's what you'd be doing. Like I wrote before, I would generally not recommend the Appalachian Gap for RVs, even though it is safely doable with proper care.
US2 and US302 I'd expect to generally be in fairly decent repair, but I don't travel them too frequently and so can't be specific there. They're rather important secondary truck routes (US2 in particular), and so kept in pretty good repair. Naturally there will be some areas better than others, and quite likely a few spots of construction along the way. The Kancamagus Highway was in very nice condition the last time I drove it, too.