Bethel VT to Queensbury NY

That route sounds good. 107 was almost completely rebuilt after Irene. I'd stay away from the 89 to 4 route becuase it means you'd have to go thru Woodstock. It's not really big rig friendly.

They are two lane country roads, except for 4 between Rutland and the NY line, which is 4 lane interstate. You should have no problems. Trucks use them all the time. Pretty good pull on 4 east of Rutland, but again, should be no problem. The good thing is, that it gets progressively better as you go from one of those routes to the other. The only real alternative would be to take 89 from Bethel to Quechee and then take 4 west. A little longer, but perhaps a bit faster.
Travel safe - enjoy the scenery.