Another option is (walking or metro) to Rubras/Vilar do Pinheiro metro to Rates to Barcelos.
The central camino from Porto is a bit industriall/urban, but not dangerous. Plus you'll get the satisfaction with the achievement of walking all the way from Porto cathedral.
Also, a camino is not just about the scenery, but the inner journey, and appreciating the beauty in all things.
For example
When I did my central camino, I had a rest day in Porto. Had originally planned to have a full rest day and metro to the outskirts. Changed my mind the day prior.
I woke up early on my rest day, left my main luggage at my hostel and walked along the camino for a few hours to Mira Maia shopping centre, felt that was enough for the morning, then walked to nearby Pedras Rubiaes metro station.
Metro back to town, then spent the afternoon and evening enjoying Porto.
Next day, metro from city, to Pedras Rubiaes, rejoined camino, then Rates, then Barcelos.
It made the distances a bit easier,, and I don't regret the city bit.
EDIT
Have already done the coastal camino, so opted with just the central this time
Both paths have there merits.
The coast is pleasant, and so is the walking from Vairao onwards.