We stayed at Casa Rietsch for two weeks and would really recommend it. We decided to stay in Matosinhos (instead of Porto) for the vicinity to the beach. It is a 3 minute walk and the beach is great. A supermarket is also right around the corner. Matosinhos as a city is not really picturesque but has nice corners and tons of (fish-)restaurants. The metro and bus stations are very close and it takes about 30 Minutes to be in the center of Porto.
The host at Casa Rietsch is very friendly and helpful. He hangs around at breakfast, gives tips and answers questions. Breakfast itself is basic but was totally sufficient for us to start the day. There are three nice ladies who keep everything very clean and tidy. The beds were really comfortable (which can be an issue sometimes). Our room was small but had a very nice bathroom. For two weeks we had a little too much clothing for the shelf provided as a wardrobe. There are electric bikes to rent which we did for 2 days to cruise along the coast.
Altogether, if you want to avoid huge hotels and prefer a cozy and private atmosphere, you are right at Casa Rietsch.