Porto housing is more affordable versus Lisbon objectively. From a climate risk perspective, my recommendation is the land area from Porto all the way east to Spain (roughly Parque Natural do Douro Internacional) and then north up to the border with Spain. How close you stay to the ocean is a function of personal preference. My mental model is "Where would I procure a residence with a low fire low climate risk for the next ~100 years?" in that area. Distance to grocery, coffee, airport, train station, and availability of fiber connectivity are also potential concerns. Population density is low in this area if that is relevant.