Does anyone know how difficult it is to drive from outside of Paris to Toulouse using backroads most often?
I haven't driven from Paris to Toulouse, but I've driven thousands of miles of back roads in France and found it to be super easy and very fun.
France has very good roads, so you won't find driving difficult. A GPS is useful for making way through towns and cities and getting notice of upcoming turns on the smaller roads.
Not difficult, but loooong! Bring a GPS and a backup map. And if you've got backseat passengers, bring some Bonine. Some of those backroads are nausea-inducing!
Just a thought, but if you can get your hands on the old Blue Guides to France, these books gave details for people doing driving trips all over France. When you come across an old town, ruins of a castle, ancient church, etc., this is the guide book that will undoubtedly identify the site, give it's history, and tell you what art works, etc., and worth stopping to see.
Very easy and enjoyable, but keep in mind that you will likely average about 35 miles per hour of driving, not counting rest stops.
I think Randy's close on the speed, but it might be even slower. The question is why? You'll be turning a half-day project into one that takes almost two days without giving you much to see except endless back roads. You'll save some tolls, but gas costs will creep up a bit, you'll have to buy more meals, and spend the night somewhere. There's nothing wrong with back roads if they go somewhere. This ain't the place to do it just for the heck of it.