I met a few pilgrims who gave up on the coastal route and switched to the frances because they were tired of the bed race
During the busy season, there's a lot more reservation on the Coastal than elsewhere, however last Autumn I did end up sleeping in a few Albergues that were either fully booked or are nearly always so, just from turning up and some people cancelling, or being lucky on that particular day in places that usually have zero beds available (that happened half a dozen times).
More often I would get in simply because my bad knees at that particular period of my last Camino, combined with the heat, were leading me to stop early, so that I was getting into places with few beds available, which was the norm for most Albergues -- there are very many with only a small number of beds.
The one really bad spot was Redondela, where the huge numbers from Vigo and the Central combined to make everywhere 100% bang full, dozens of pilgrims preparing to sleep outside or getting taxis ; but even there, my ginormous credencial + inflatable mattress led to my getting a spot on the floor at the Parroquial by exception to normal rules in that place, where I slept very well, good shower, and machine wash for dirty clothes.
I slept in the garden of one Albergue at Caminha, outdoors a few times, in the street in the rain at Porto.
So ? I survived ... An inflatable mattress is good weight to carry (though sadly mine deflated at some point after leaving Santiago, so it just became a sleeping mat on the Francès, but I'm definitely getting a new one for my next pilgrimage ...).