Congrats on the trip! If you like France, you're gonna love Norway
Best time of year is actually now, because over the last few weeks everything has turned green after a long winter and all the flowers are blossoming, end of may/early june are absolutely fantastic over here.
Pretty much everything here is scenic, but just to highlight a few stretches that I've driven:
Fv51 between Fagernes and Vågåmo
Fv55 between Lom and Sogndal
E6 from Lillehammer to Dombås
E16 from Lærdal til Bergen via Voss
Rv15 from Stryn to Byrkelo
Fv63 from Åndalsnes down via Geiranger to Rv15 (very touristy in summer, but for a good reason!)
Fv64 "Atlanterhavsvegen" from Kristiansund southwards, with the famous bridge
These are just a few to get you started, from the top of my head. Basically, you can't go wrong here as far as scenic drives go. I'm probably a little bit biased but even if you'd correct for that it's still pretty amazing!