Where in New England are you headed?
I'm in Vermont. I tend to use I-87 and I-88 to get to I-81, catching I-87 most often around Lake George, NY. That's not so convenient of a route for e.g. the Boston area, but would be workable for most places in northern New England.
The US highways are generally acceptable for RV travel, though some may be slow or rough in places. Most of the state routes in New England are also OK, but there are some big exceptions that are definitely not good for RV travel. A couple of examples, not the only ones, include VT 17 across the Appalachian Gap (between routes 116 and 100) which would be better avoided, and VT 108 through Smuggler's Notch (between routes 100 and 15) should positively not be attempted with nearly any RV. A few big trucks or motorhomes manage to get wedged between the rocks in Smuggler's Notch most years.