The Companha station is the only one gong to Lisbon I believe. From the Sao Bento station, you can take any train over to Companha at no additional cost. We elected to take. taxi directly to Companha even though the train transfer was free, and it was further away. It turns out that the area near Sao Bento is always teaming with traffic and construction 24/7 and it was faster and more certain to just go straight to Companha - where the driver can take a freeway.
I don't feel the city requires much of a tour. Essentially everything is along the two sides of the river and the bridge between, and the area over to Sao Bento. That whole hillside between Sao Bento and the coast has some interesting streets.
I did note that they do not seem to have any idea of how to make a capuchino in Porto - every one I bought tasted horrible. But it's the price you pay to sit down and possibly hear a concert by a singer with acoustic guitar.
We were considering the river cruises, but they seemed to be more of a gimmick We have seen the other bridges during various train rides and taxi rides, and the only interesting place is by the main bridge where everyone is hanging out.
Be prepared to do a lot of walking - and have the Bolt and Uber apps on your phone, or possibly use a taxi.
Consider some day trips out of Porto.
