> Your best chance of seeing interesting things as well as interesting buildings...

> Your best chance of seeing interesting things as well as interesting buildings seems to be to look for privately-owned/smaller castles that are open to the public.

Some very nice ones are the Chateau d'Abbadia (https://www.google.fr/search?q=chateau+d'abbadia+intérieur&t...) ; Dampierre-sur-Boutonne has some original stuff preserved too (https://www.google.fr/search?tbm=isch&q=dampierre+sur+bouton...)