I've been a bit reluctant to comment here before because as a visitor to the US I can't claim to know the coastline as well as someone who lives in the area, but over a number of trips (over probably 30+ yrs now) I've covered most of it from northern Maine down to around Orlando.

For the New England section - roughly New York northwards - I think you'll do well to find any sort of 'scenic' route that stays near the coast until you get up into Maine and past Portland. 'Scenic' is of course what you make it and on our last trip there (we were heading south) we rode the length of Long Island just to look at what was there. Not quite pristine wilderness to say the least. but interesting in a kind of 'social tourism' way. North of Portland there's loads of little inlets and peninsulas that are fun to ride - Mount Desert Island and Bar Harbour probably being the best known of them - but in the summer (good luck doing it in winter) it's a tourist area so blocked up with RVs etc. We found inland - around the White Mountain area of NH - a much nicer area to ride, and particularly the finger lakes area of northern NY state.

South of New York is pretty awful - that 200+ miles from NY down past Washington is close to my idea of hell on earth. Last time we were heading south we went east of Philadelphia through the Wharton forest and took the Cape May ferry. The coast there is pretty much a ribbon development from New York down to Atlantic City so best avoided. Hit a holiday weekend and the traffic is stationary. The ride down through Delaware to the Chesapeake bridge / tunnel is pretty good - if you've come from the north you'll notice the drop off in traffic density after the ferry, but it does dump you in Norfolk. The one 'must do' bit for me though was after that - riding down the Outer Banks islands and the final ferry from Ocracoke to Cedar Island. That whole stretch down to around Wilmington was probably the area I've enjoyed the most.

The whole of the Chesapeake Bay area has a kind of 'weekend away' feel to it. There's loads of parks, campgrounds, clapboard fishing villages with rustic restaurants etc lining the coast. It's far from wilderness but it is the US leisure industry on a large scale and worth a visit. I suppose 'nature with facilities' would sum it up and that's what a lot of people want from their time off.

We were meant to do the SC + Georgia and down to Jacksonville section last year but Covid killed the trip off. Florida - from Jacksonville to Orlando anyway - is ok but very bucket and spade touristy and too humid for me (in the summer anyway). There's a few tourist things to do that are worthwhile that Jenny mentioned - Daytona, the Kennedy Space centre, both very much semi mythical places from the past (or my growing up in the UK in the 60's/70's past anyway).