Whatever you do stay off 22A. Think of it as a two lane Interstate with no shoulders. Everybody (including me) drives over the posted limit. The police have had a bit more presence the last few years so, the speeding is not a bad as a few years ago but still not a good place for a bike. Route 7 has two lanes but shoulders for most of it's length. If you start in Manchester, the four lane portion will be south of your start point.

If time is not pressing, IMO the best option would to stay on 7 till Brandon and then head over to Lake Champlain. The Green Moutain Bike Club has some routes posted on the website that go down in that direction. Do a connect the back country roads from Brandon to one of our routes. Would be the most scenic and much less hectic. Hope that helps.