That's as many as N100, N800 and N1000, just two. At least with can juice up more cars to from N500 and N600, I don't believe you can do the opposite to downgrade N200 cars to N100.
You have about road legal cars in the game, across 9 different sub categories (including the "homologation specials"), it averages a little more than 5 cars per sub category. The N200 and the N500 are overpopulated, obviously some categories will have a small number of cars.
The worst part is that the categories are BS, as they are based on maximum power, not power to weight ratio. If so, the car groups would be completely different. The N700 it's a perfect example. Never driven the Charger nor the McLaren to access the performance, except maybe in some challenge, but I'm pretty sure no even remotely close of being matched.
The Charger has a p/w ratio of 0.354 hp/kg, closer to Porsche 911 GT3 RS (N500) 0.346 hp/kg or Mercedes SLS AMG (N600) 0.352 hp/kg. The McLaren 650S has a ratio of 0.482 hp/kg!
The Corvette C7 (N500) as ratio of 0.424, near the Viper GTS (N600) 0.411 or the Lambo Huracan (N600) 0.423.