Reddit mentions of The Way Of St James: Pyrenees- Santiago, Fisinsterre : A Cyclist's Guide

I cycled the Camino back in 2010. It was a great experience but I agree with what others here have said and that is you should avoid the walkers paths as much as possible. It is unfair to keep "running over" people and it messes with your rhythm having to keep stopping and starting to dodge other pilgrims.

I'd recommend this book as a guide. The author has plotted a route following the Camino Frances as closely as possible to the walking route, but on the roads. Often the road you cycle will run parallel to the walkers route anyway. Also the roads in Spain have been heavily invested in so most traffic uses new motorways, leaving the old main roads virtually empty. Spanish drivers are also very courteous to Camino cyclists - probably to avoid damnation by hitting a pilgrim with their car!
Didn't really use albergues as we wild camped a lot of the time but there is plenty of oppurtunity to meet others in the numerous cafes along the route, and in the cities etc.
best of luck with whatever you decide!