I am puzzled by the reference to the Appalachian trail.

I would suggest considering using the Adventure Cycling maps for the part going down the coast. The AC maps have a lot of useful info like locations and phone numbers of services and points of interest.

You mention a lot of major cities, many (most?) bicycle tourists generally avoid major cities hitting mostly rural areas and smaller towns. I think the Atlantic Coast Route may adapt well for you in that regard since it goes not too far from Philadelphia, has an option to go through Baltimore, and goes to Washington DC. In North Carolina it has an option of going along the barrier islands or taking a more inland route.

If you are passing through Baltimore and need a place to stay or other assistance, let me know.

Have a great trip!