Our Spain eSIM runs on Movistar and Orange Spain, both on 5G. Those are two of the four national networks, so you get the same coverage a Spanish subscriber gets rather than a restricted visitor layer.
Spain has some of the best mobile coverage in Europe. 5G is live across Madrid, Barcelona, Valencia, Seville, Malaga and Bilbao, and 4G reaches almost everywhere else including most of the Camino routes.
The genuine weak spots are the Pyrenees, parts of inland Extremadura, and the mountain roads of the Sierra Nevada. Download offline maps if you are driving those.