Accordingly, the 2017 and onwards RC's were updated here and there, mainly due to major - major - reliability issues (valve/cylinder clearances, blown head gaskets, electrical issues, stalling and overheating).
After reading, watching, testing and inquiring for two months (more or less every day), my personal conclusion is that nothing has changed on the 2017's in terms of reliability issues. Sure, it has the 320 mm rotor, slipper clutch, different exhaust and hence better clearance for track, but honestly in my mind it's not in the same league as the N400 (although the gearbox on the N400 seems to have some bugs here and there, remains to be seen).
A triple clamp and climp-ons and the ride is similar if not better on the N400 for track work. Ones saves money and time purchasing the N400. Just my two cents.