We walked along the bank of the Mino. It was easy and you can find albergues between Caminha and Tui.There are two main options for returning to the central from the coastal in time for Tui. The most common is to make the switch fairly early at Vila do Conde, joining the Central in Rates. The other option is to continue on the coastal until Caminha, the last town in Portugal on the south bank of the Minho/Miño river. You can then follow the river to Valença and cross it into Tui.
We did the option along the River Minho and really enjoyed it taking several stops to swim as it was sunny and quite hot. We stayed for the night at a hotel in Valenca as we wanted to explore the impressive fortress and it was worth it. But if you want to meet your friends in Tui then probably you'd like to walk on, cross the bridge to Spain and stay overnight in Tui which has also interesting sights to explore closer.There are two main options for returning to the central from the coastal in time for Tui. The most common is to make the switch fairly early at Vila do Conde, joining the Central in Rates. The other option is to continue on the coastal until Caminha, the last town in Portugal on the south bank of the Minho/Miño river. You can then follow the river to Valença and cross it into Tui.