I my experience, changes to the daily route do occur but rarely is it a "major" detour. The inability to to predict where and when a particular meal will happen is more likely caused by punctures, repairs or just "having one of those days" when you check to see if the brakes are dragging.

My system is to carry the paper maps in the bottom of a pannier, On my tablet I use Locus, a mapping app that allows downloading and saving maps at any level of detail you want. Prior to the tour I save the whole route if a week or less otherwise I just stay a week ahead based on my speed and plans. I save the area near the route with high detail and surrounding areas with less. The GPS in the tablet shows my position and direction on those. I also have all of the map/information panels of the ACA maps I own scanned in for when I am on one of their routes.