The first major city on the Camino Primitivo is Oviedo and this Camino then continues on, through the mountains, to Lugo and from there joins the
Camino Frances at Melide. The Camino del Norte actually coninues along the coast through Gijon before turning inland and going through Miraz (where the 2nd CSJ albergue is) and joining the
camino Frances much closer to Santiago (I think it is somewhere near Arca but not sure on that one).
The Camino Primitivo goes through some quite mountainous areas - especially if you take the Hospitales route - and is very beautiful. It is quite remote in parts and the albergues / accomodation, though adequate are even less than on the Camino del Norte earlier. I travelled on the Primitivo instead of continuing on the del Norte when I followed this way. I actually researched both ways and left my options open until I got to Oviedo before making a decision. Oviedo is not, strictly speaking, on the del Norte but some pilgrims detour there before returning to the del Norte path again.
Hope that clarifies, Janet