Lurdes E Jorge’s place was great for two people! It was a private one bedroom a 15 minute (uphill) walk from the river. The bed was comfortable and there was plenty of room with the empty walk-in closet. The second bed is a pull out couch in the living room. It was comfortable as a couch, but may be a small space with 4 people in the apartment.
The space was great, but it is definitely worth noting that Porto is a hilly city and the apartment is a 10-15 minute walk uphill from the centre of town. Worth noting for those uncomfortable walking up hills, though, Porto is not a great place for those uncomfortable with hills.