It is Romneya coulteri, aka California tree poppy. In the same family but a distinct genus separate from California poppy, Eschscholzia californica.

is it medicinal like the conventional calif small orange poppy, analgesic uses? as a tea? of the flowers?

No. While generally considered nontoxic, it does contain a number of alkaloids that can cause digestive upset. And it has potential for contact dermatitis in those that are sensitive.