Hi I cant help you with the first two, Lyon and Le Puy or the crossover from St Jean but if you havent already posted on the Le Puy thread then other forum members will be able to help you with info on that part.
The Norte is quite a pleasant walk, by the time you hit it you will be well walked in and the sharp ascents and descents of the first sections should hold no worries for you. There are many outstanding albergues along the length of it, Pasajes, Guemes, Boo, Casa Belen, Miraz and many others. It was well waymarked in 2012. There are quite a few variants some not listed on any guides, if you have a maps of where it goes near the coast you can choose your own ways of walking along the coast and sooner or later come back to the camino, from a book I have dated 2002 it seems on one section in Asturias that the camino closely followed the coast however the camino in that section now goes inland, probably because an Albergue was opened and the camino was changed to go by it.There is a lot of Asphalt some of it on hard shoulders of busy dual carriageways, a lot of Urban Centers to go through until about Aviles, But there is some outstanding natural paths through areas of jaw dropping beauty.
To continue with the theme of the camino over time being diverted on to other ways, the highest point on the Norte,Serra da Palancas, has been almost abandoned and pilgrims are instead sent down 24 km of an unused road between Soto de Luina and Cadevedeo, however the Palancas route is mostly off road on an old cattle droving path, some pilgrims still use it against local advice- but say that way is often the outstanding section for them of the whole Norte, it has a clear viewpoint at the highest point of the whole coastal area around.
It rains a lot on the Norte, but so does everwhere at the moment.
It has a celtic feel to it due to the strong connections of Asturias and Galicia