Bom dia Lorenz
In May 2016 we walked from Porto to Matosinhos on day 1 & returned to Porto on the Metro from the Mercado stop.
On day 2 we walked from Matosinhos to Vila do Conde & again returned by Metro. (Be sure to cross the river in Matosinhos on the R. Congosta do Abade near the Mercado. We missed the signs. The extra 5km hurt by day's end!)
Some recommendations for accommodation.
Esposende, Hotel Soave Mar.
A Guarda, Hotel Convento de San Benito.
Oia, Casa Puertas.
Redondela (4km out of town) Hotel Antolin, Cesantes
Pontevedra, Hotel Restaurante Rúas.
Padrón, Pension Jardín.
Santiago, Hospederia San Martin Pinario or Hotel Costa Vella.
There are no cafés or shops between A Guarda & Oia - stock up before you leave! Also - there's nowhere to eat in Oia on Mondays (other than Casa Puertas).
Our walk into Vigo was endless, passing through industrial zones and dockyards for more than an hour. If you can find a way, it would be better to approach Vigo other than by the coastal roads.
Bom caminho.
Michael.