First, welcome to the ACA Forums.
The problem with a route along the eastern seaboard is that the various routes have different issues. ACA's Atlantic Coast Route (AC) route tries to avoid heavy traffic and congestion by heading inland which takes up a lot of miles. The East Coast Greenway (ECG) does the more direct route method, but they use some extremely heavy traffic roads (they call "high stress roads"), many of which I think are extremely poor choices for bicycling much less touring. Here is the ECG map:
https://map.greenway.org/ .
I did the ACA's AC southbound way back in 87 as part of a USA Perimeter tour but traffic has obviously only increased since then. When I rode the AC, I broke off in Washington due to all the traffic and hit the Blue Ridge Parkway until I got to around Blowing Rock and headed back to AC route as I had to visit relatives in Columbia, SC.
You don’t say where you are leaving from in Georgia, but I will assume Savannah since that is where you ended your previous trip. If I were doing it, I would head up on ACA’s AC coast route to Virginia Beach and then take ACA’s DelMarVa Route to Lewes, DE, where I would take the ferry to Cape May, NJ. From there, I would create my own route and go inland a little and take the various rail trails and less-traffic roads (RWGPS’s or Strava’s heatmaps are great for this) up to around Lakehurst, NJ. I would stay off the coast mostly due to traffic and congestion; just not my cup of tea. From Lakehurst, I would connect to ACA’s CNYC route. Take that north through NYC (uses trails) to near Poughkeepsie where I would rejoin the AC route to Bangor.
I would definitely review the routes using AADT maps and Google Maps’ Streetview to ensure that traffic has not increased beyond your comfort zone since the routes were last updated.
Good luck and stay safe!
Tailwinds, John