I have to say that the walk from Porto to Vilarinho was the most stressful day on the CP. I had already walked from Lisbon so was fairly seasoned. I had opted for the inland route because the weather forecast was for wind and rain which didn't encourage me to take the coastal route. There are various options out of Porto, including public transport. I chose to walk and although it was difficult , due to suburbs, industrial areas, road walking, I would always choose my own feet over transport, but totally understand that this option does not suit all pilgrims. I wrote about this stage in my blog
here - take a look to get an idea of what is involved. But also do a bit of research on this forum to discover what options are available, including
@peregrina2000's guide that can be found in the resources section.
Bom caminho