Would absolutely stay with Luis again! His apt is in a quiet neighborhood with a cute cafe (with a super nice waitstaff!) down below and a grocery store a few minutes walk away. It's not in the middle of the city but it's really easy to take the bus from outside his front door to downtown in about 10-15 minutes. Luis will give you a map and a list of all local attractions and how to get there by bus and subway. He also makes you breakfast every morning and is super available to answer questions and give advice, but will give you your space if you want it. Luis will also give you rides around the city and to the airport for cheaper than the cost of a cab which was a huge perk for us.
My cousin and I had a blast in Porto and are so glad we found his Air Bnb to make our stay even better.