northern part seems correct to me.
southern part have some odd choices IMHO and a few incorrectnesses -in regards of historicity and precision, if it is your aim, unless you can ignore my inputs here.
-Tursan should be much more tiny : just a little blob at the south of the city of Mont-de-Marsan. The latter should be in Marsan though. Or call Marsan another way (Albret can fit). Not sure tursan is important enough to be in though.
-Marsan goes far too north. Vanilla borders for Bordeaux were pretty correct on this regard.
-Gévaudan vs Melgueil distribution looked better in vanilla. Maybe split Gévaudan between, north, Gévaudan, and south, Nîmes/Lodève/Alès/Uzès.
-Savoie county is modern Savoie district that doesn't fit exactly with the period, one part goes accross the Rhone river, where the city of Belley lies in southern Bugey (so it make your Belley province's name incorrect if you tweak the border : Bresse or Bugey can fit here)
-Genf, goes also accross Rhone in its northern part (pays de Gex mostly).