Hi, you’ve got
Brierley as a guide, with both routes marked, so you could just start walking from Porto along the river, and keep going until your time runs out and you need to get a bus or train.
No need to plan, just know where your accommodation options are, so if you want to walk further each day you can, or if you want to stop and overnight with new-found friends, you can do that too.
It’s all fairly level and easy walking (unless you get hit by very bad weather).
There will be other pilgrims, but not lots, so don’t worry about not getting a bed.
I’ll be walking from Porto to Santiago, 12 to 28 Sep, along the Senda Litoral, which joins up with the Coastal in several places (for example, between Esposende and Viana do Castelo, where there is no continuous path by the sea), so might see you.
Bom caminho!
Jill