When I read "walking the Salvador backwards" I heard myself say "no, no, no". This is a route I want to do and will do, but after having walked enough Camino km I know my limits and know I am not comfortable walking it alone, let alone against the waywarkers.
Second thought is that. Camino is so not about the tourist attractions that may be foind along its way. Now, if a long distance walk is what you are interested in, then yes, views and sites are lart of it, but a pilgrimage?
If site siteseeing is important to you, well, you will miss out on what is on the other route nomatter what. The Norte takes you through San Sebastian, Bilbao, Santander, Santillana, Guernika. The food is 100 times better than what you will find on the Frances. And you will get the coast.
Walk the Frances and you walk through many old towns whose history is tied to the Camino, lots of religious architecture also tied to the Camino. You walk through San Sebastian, Pamplona, Burgos, Leon, Astorga.
No matter what, you will miss out on something. Which is why so many go back year after year Nd discover a new route.
The question to ask yourself is what do you want from this walk? The Frances will give you a chance for many more encounters, it is more socialble, you will have people walking in frint and behind you regularly, and lots of known faces at the bars when you stop for a rest during the day. Walk the Norte and enjoy walking alone, while meeting uo with others in the albergues in the evening and enjoy the coast, Basque food, and just as wonderful cities and towns to walk through.