on the west cost IMHO (having traveled it several times) the coast is best travelled and viewed going north to south, Most turnouts are on the ocean side and angled for traffic coming from the north. Makes viewpoints difficult going south to north. and easier to see going north to south. Especially true on highway 1. Did San Diego to cresent city once. Luckily we live in northern oregon so North to south is easy.
I don't know about the east coast, but first thought is south to north would be my choice.
So consider going west across canada, great scenery then head south around Seattle.