I did that that route in April this year. About half of Albergue’s were closed until after Easter. Even cafés and small stores were often closed or had short hours in the smaller towns. Hotels and pensions were open, though.
On Easter weekend you should have bookings, but otherwise I didn’t find it a problem at that time. There weren’t crowds at all.
It changes from year to year, but the weather was absolutely glorious. I had one day of torrential rain, but otherwise it was perfect.
Just to show you that different pilgrims can have different experiences on the Camino, here is my experience:
I left SJPP on Tue, 11 April ’22 (The Tue before Easter Sunday). The albergues in Roncesvalles, Zubiri, Pamplona we’re busy, but open. I had made reservations for the first week, but had no problem doing so.
I did not observe any significant # of closed albergues…bars, restaurants, food stores, shops were all open and anxious for the pilgrims’ business as it has been a lean past couple of Covid years. There may have been reduced ‘Open’ hours, but not having been there before, I don’t know what their previous hours were. Remember that Spain observes a daily siesta from 2:00 - 4:30/5:00 when virtually ALL businesses are closed.
The weather was the typical ‘spring in Spain’. Cold, often overcast mornings, occasional spring showers, some lasting most of the day, but I never experienced anything even close to “torrential“. The Camino population was not noticeably crowded, but albergues ranged ~75% - 90% full (my estimate).
I would suggest reconsidering the aggressive plan of walking over half of the Camino in just 2 weeks. That’s almost 450K; averages over 30K / day in 14 days. The Brierely book steps for that distances takes almost 3 weeks. And thats walking that distance EVERY day! You might miss some things the Camino has to offer with such an aggressive plan
Buen Camino!