Looking at Stoner’s route there are a lot of busy roads with no alternative especially in Spain. The part you liked most was where you were on quieter roads Stoner. I’m sure that if you’d sought out minor roads more you’d have found other sections just as good.
We buy detailed maps as we go or follow véloroutes which are either dedicated cycle paths or quiet roads – though some can be busy peak season especially on the west coast in Les Charantes. They offer easy riding if you are loaded.
https://www.francevelotourisme.com/base-1/itineraires
We travel very light: no stove, 1.8kg tent, just rear panniers. Mountains are still are chore though. If you want to cross the Alps or Pyrenees then stopping in hotels, gîtes etc. means a bar-bag or seat-post bag is big enough.