While I am probably too far down the list for anyone to read, I shall venture forth regardless with my personal observations and recommendations based on first hand experience. I started my 1st (of 4)
Camino Frances at the tender age of 70 years, 7 months, (solo) with a pack weight of 4 kilos, 4 May, 2015. My intent was to walk about 25 km a day. With my pack, and two trekking poles.
I though I had done my homework well, and was willing to go along with the oft expressed "go like a pilgrim, don't worry about finding a place to stay." Well, that worked, but no so well. I really did not know much about reserving ahead.
I was second to last arriving at Zubiri and was just able to get a bed at the municipal albergue. Had to wander a bit in Pamplona to find a bed in a private albergue. Logrono was an exercise in frustration, following the map provided at the Pilgrim's Information Office. Fortunately a fellow pilgrim that I had met the day before took me to his albergue. But it was not until Najera were I learned the true value of making reservations ahead.
I arrived at the albergue first, before it opened, and put my pack by the door, and went to sit on the stone wall to await opening. By the time it opened there was a line of pilgrims but no worry, I was first in line. Not so fast. When the door opened and we entered the nice young lady asked the assembled masses which of us had reservations? Reservations? About half. When she had settled the those with reservations she came back and took the first four standing patiently in line. I was one of the four. The rest had to go in search of other lodging. After checking in I went back to the front desk to ask about "reservations". She explained the system to me and gave to me a recommended name and number.
From that time on I made reservations ahead. On that first Camino I reserved about 5 nights ahead. On numbers 2, 3 and this last one, Oct - Nov 2021, I reserved the whole trip in advance. Worked like a charm. Especially for this last one which I started just days after turning 77, and lots of services along the way were shuttered for the rest of the year. Having reservations in advance gave me the opportunity to give to my beloved wife a complete list of where I would be and how to contact me should she need to.
I have used both Onlypilgrims.com (Jesus) and Booking.com with great success. Jesus helped me a couple of times when I needed someone to speak Spanish beyond my limited ability. My personal experiences are different than others, but for me...your Camino is your Camino. Jesus is hot on my next planned Camino, April - May, Lisbon to Santiago. Buen Camino.