That depends of the amount of pilgrims on their way that particulary time and the time of the year.
Speaking about Fernanda's, that is a popular place to stay.
People walking from Barcelos find an albergue at 10 kms from Barcelos ( Tamel) and think it is an other 8 kms or so to Fernanda. Then they arrive and it is full .
The options are go back to Tamel, or another kind of bed and breakfast 3 kms further in Vitorino dos Piães with a few beds or 6 kms further on a more luxury bed and breakfast in Facha with some beds . Then the other option is to walk on to Ponte de Lima what means that you will walk another 7 kms or so. The distance between Barcelos and Ponte de Lima is about 32 kms.
Fernanda always is prepared to call ahead to her collegues if there is still a bed available.
Fernanda has 10 beds in the albergue (a gardenhouse) a room for 3 in the same gardenhouse and a veranda with a bed only underneath the roof but further fully open . In summertime people love to stay there.
And she has 2 rooms in her house, one with a double bed and one with two separate beds.
Lots of people book in advance Couples mostly choose if available for the dorms in the house.
When you book in advance Fernanda asks for your first name and the country you are from. That she notes in her reservation book. So a random day she knows that will arrive e.g. 2 from Germany, 5 from the USA ,2 from Australia and 1 from Portugal etc. That's all. If you do not show up , no bother.
If you walk in a more quiet time like we do from monday next -we leave for Porto tomorrow and arrive at Fernanda's Saturday next., and we see few pilgrims on the road going together with us, there is a better chance to find a bed but knowing the week after and already being in Spain , realising it is Semana Santa, the week before Eastern , we have booked ahead because we expect a lot of mainly Spanish walkers and Portuguese bikers going into the same direction as we do.
Specially for Tui to Santiago we already booked in October last year.
So what to do is up to you.
I know Fernanda since some time, stayed there for weeks and saw it happen every day again.
Bom caminho and hope you will like your stay at
Casa da Fernanda.