Were Portuguese ships like Spanish galleons?

Can studies of Spanish galleons be used to understand Portuguese ship capabilities?

Yes, with a caveat: Portuguese ships tended to be slightly larger because Portugal designed for the Atlantic while Spain also had to consider Mediterranean service.

Spanish galleons offer a reasonable starting point for understanding contemporary Portuguese ships, though Portuguese examples were usually somewhat larger. Spain had to think about both Atlantic and Mediterranean requirements, while Portugal's naval activity was centered much more completely on the Atlantic. The small design differences followed from the operating environments each monarchy expected its ships to face.