Loire ... et plus? 17 days.

Week cycling in Loire is great

https://community.ricksteves.com/travel-forum/france/normandy-brittany-thoughts

There's Burgundy too.

Either choice is a good one. After all those Renaissance chateaux, do you want to revert to medieval castles and prehistoric cave art in the Dordogne? Or WWII sites and Romanesque churches and prehistoric stone circles in Normandy/Brittany? Foie gras and good local wine in the Dordogne, or apples and cider, but no local wine, in Normandy/Brittany? I can't choose for you, but I can agree that you're right to choose just one, not both in the week you'll have. And I'd recommend a car in either, as in the Loire also.

If you're looking at early spring, weather might be the tiebreaker -- likely to be better in the Dordogne. But of course anything's possible and you can't wait for a specific forecast to make this call.

I cycled along the Loire River Valley Bike Trail from Orleans to Angers and was sorely disappointed. Shortly after leaving Amboise, it continually meandered up some hills to the south, through various farmers' fields and villages largely out of sight of the Loire. For better scenic opportunities, I suggest sticking to the roads paralleling the river.

Loire Valley is great, go to several Chateux. We stayed in Blois.

There was no Loire bike path when I cycled. I used the white roads on a Michelin 1:200,000 map. Virtually traffic free

Dick, David & Tim ... Thank you for your suggestions.

-F