For the Salvador, I used maps.me and downloaded the GPS file for all Caminos in Spain from this forum. But I will say that there were a few places on the Salvador where the track led me astray. There were a couple of spots where the route had definitely been changed since the track was made, and there was once where the person making the track simply took another option from where I wanted to go, and this caused me quite a bit of extra walking. I simply missed the sign to the village where I hoped to spend the night, and continued straight, which is where the GPS track went. The track gave me false confidence in being on the correct route!
Most of the Salvador is well marked, but there are several spots that created some confusion. I did meet other pilgrims that were quite frustrated by the time they arrived at the albergue, after spending a lot of time trying to figure out where the "correct" path was. The locals are always helpful, but in some of the little towns it was not easy to find anyone!
I'm not familiar with the Vadiniense. Buen Camino!