I wouldn't worry about traffic west of the Connecticut River in the Berkshires, even on Route 2. I don't live there, but the rides I have done in northwestern MA have been nice and traffic has never been an issue. I rode Route 2 from North Adams to Charlemont years ago and it was a beautiful ride, much of it along the Deerfield River. I believe that section is still part of the annual Mt. Greylock Century ride. A popular club ride climbs Route 2 from Petersburg, NY to Williamstown,
MA over Petersburg Pass, about a 1500' climb, and returns to NY via Route 43. Route 43 from Williamstown, MA to Stephentown, NY is flat and a nice ride. I have no recollection of Route 2 from Petersburg to Troy, NY. Route 43 from Stephentown to Albany is a decent ride, but you have to cross a series of small hills. You'll probably do about 1200-1500' of vertical in that section.