No restrictions really, classes are determined by drivetrain, actually it's just 2WD (FWD and RWD in one class) 140 tread wear tire or higher, AWD class 140+ tread wear and Unlimited class (any drive but specific rated tires).
So power is not restricted, usually the course layouts big power is not needed. Competition in 2WD class would be type-R hondas, rx7, Silvia. I figure a DE is just a bit underpowered, the VE in a lightened B13 with good suspension and brakes would be perfect balance.
We're a small island we don't have 100's of racers showing up, so to get specific with classes is not really possible. Usual turn out is maybe 10 racers per class.