I walked the Central Route earlier this year, after walking from Lisbon via Fatima. I chose not to skip any sections. Certainly the stage from Porto north lacks the aesthetic appeal of the city and you don't reach the relative calm of farmland until much later in that stage. But it is where many Portuguese live and work, and I thought it would be disdainful to ignore that, and them, in my own pilgrim experience. After all, there is little of the countryside that hasn't been altered by the hands of man, as have these urban landscapes.
My target was to walk about 20 km stages, and I was largely successful in doing that. Most days I chose to book ahead, and this sometimes required more expensive accommodation than I had wanted to use in order to keep my distances manageable. If I was doing a shorter stage, and was confident I would arrive early enough to get a bed at a place that didn't take bookings, I did that, but only in a couple of places.
This was in May, and from Porto there was some evidence that there was a bed race underway to get to municipal and fraternity albergues. For example, at Ponte de Lima, there was already a substantial crowd at the municipal albergue waiting for it to open when I passed it early in the afternoon. Perhaps not enough to fill it completely, but enough to think that there didn't need to be many more pilgrims arrive to do that.
I didn't take a rest day after Porto - I had taken one there before starting on this section. There are places like Valenca/Tui, Pontevedra and Padron where there was a lot to see and where arriving early to allow for more exploring, or taking a whole day might be considered.