It will be me and my wife. She loves wine and we want to visit some wineries. Should we stick to these two cities and do a couple of day trips OR hit highlights in these two and stop at another city (maybe Zaragosa) for one or 2 nights along the train ride to Madrid? Very open to suggestions, This is a HUGE learning curve!
If wanting to visit wineries, consider staying in Logroño for a couple nights. There are plenty of wineries in that area.
The Madrid and Barcelona areas are not known for their wineries.
The best wine region is Spain is Rioja in the north central part of the country near Basque Country.
Barcelona and Madrid are good, if you do those cities, don't miss Toledo and Segovia as day trips from Madrid.
Next time visit the south, Cordoba, Seville, Granada, Malaga, Cadiz.
Then the Basque Country and Galacia (NW corner),
Just seven days to visit both Madrid and Barcelona will limit you to just those two cities. As suggested above, the Rioja region near Bilbao makes for a great wine country destination.
Its possible to visit the Ribera del Duero region from Madrid. Or Penedes from Barcelona. Or the cava area from that city as well. There also DOP wines produced within Madrid limits. That is the closest option.
I do not think there is one “best” wine region. Rioja is the best known to foreigners