About the ACA Northern Tier: if possible we would like to add more of Canada. So the route we are currently considering is as follows:
- leaving New York City with the NY State Bike Route 9 to Poughkeepsie, NY (85 miles)
- join the ACA Atlantic Coast to Bar Harbor, ME (542 miles)
- start the ACA Northern Tier and follow it until Ticonderoga, NY (401.5 miles)
(or maybe as an alternative route take the ACA Green Mountains Loop from North Haverhill, NH to Port Kent, NY)
- from there rejoin the NY State Bike Route 9 to Rouses Point on the New York - Quebec border (92 miles)
I've bicycled from New York, where I live, to Bar Harbor, ME, picking up the Atlantic Coast Route. I have also ridden the Norther Tier. I would not do as you plan. You'll be repeating the section in New England where both routes are the same.
I would avoid Route 9 in New York if you can. It is a very busy road. I would not follow closely NY State Bike Routes. They use too much busy roads.
If you go off and on the Northern Tier, consider including the highlights, Erie Canal bike path in New York, Niagara Falls, Canada (Falls are also in New York, but not as spectacular), Going to the Sun Road, Glacier National Park, Montana, crossing the Continental Divide.
When your plans are more definitive I can give more help bicycling in New York.