There's only one wine bar in Porto with anything like disorderly wines. It's called Prova Wine Bar (R. de Ferreira Borges 86, 4050-116 Porto).
In Guimarães, alas, there's nothing winewise, only a good cheese shop.
In nearby Braga there's a very good restaurant with a disorderly list called Delicatum (Travessa do Taxa nº 2, 4710-449 Braga). Owners André Antunes and Joana Vieira are great people and very knowledgeable about Portugal and Galicia.
Most vinho verde is industrial, though at least it doesn't ordinarily have oak or high alcohol/extraction/concentration.
Quinta da Palmirinha and Vasco Croft are two biodynamic producers that are doing the closest thing to natural wine in the Vinho Verde area.
Ponte de Lima is a charming village, Portugal's oldest, and should not be missed (Guimarães is Portugal's oldest city).
In Porto there's a famous bookstore called Livraria Lello, but there are so many tourists trying to see the interior that you need to buy tickets to enter, deductible from any book you purchase.
In Porto there's also the Serralves Foundation, a contemporary arts center designed by Alvaro Siza.
Porto has lots of excellent seafood places, but with conventional wine lists. The house vinho verde is usually a good option. Explore the red vinho verdes, made from the inky Vinhão grape, and very different tasting.
Downtown Porto has a charming street called Rua das Flores with a nice little food shop called Mercearia das Flores.
In Arcos de Valdevez, a town in the Vinho Verde region, there's an excellent naturally-oriented producer called Tiago Teles who is worth exploring. He doesn't make vinho verde, but what he does make is very interesting.
In Lisbon there are half a dozen restaurants at least with disorderly lists, but it doesn't sound like you'll be spending much time there. Plenty of other things to see and do there, of course.
If you have any more specific questions, just shoot.