Driving is shocking and that is coming from someone
who learnt to drive in Nice
whose driving as ALWAYS been qualified by british people as too european.
Roads are small and narrow and locals drive down there like you'll expect Loebs to do so.
You should be fine(ish) on the road bike, but as pointed before it's up and down and up and down.
If you have time on the way back you could pitch up the 3 cols. Park the car at isola. Ride up to St-Etienne de Tinée, up the col de la bonette, down to jaussier. Up to the col de Larche, dow the other side in Italy, and then back up to France through the col de La lombarde…
I think it's around 4000m of altitude gain.