Today 59 cars will compete through four classes
GTP
LMP-2
GTD-Pro
GTD
GTP is the top class, these are hybrid prototypes that all have the same electric motors onboard but varying ways of using those motors. They also will have different engines, from big V8s, like the Cadillacs have, to smaller turbo engines. BMW, Porsche, Acura, and Cadillac competing in that class. Lamborghini and Ferrari will be joining sooner than later
In this class you'll see some of the big names in sports car racing driving, including some from F1 too
LMP2 is a prototype class that's sort of like Indy - choose a chassis maker, use X engine, go race. It's idea is to keep the cost a bit lower (example, a GTP chassis is said to be $2M, this class is more like 500k)
GTD classes are the porsches, lambos, audi, corvette, mustang, astons, ferraris etc
They're the 'normal' cars, race versions of street cars
Pro is an all pro driver line up
the other (am) has to have varying levels of drivers (bronze to gold)
In the past the cars have been the same but with differences on tire sizes, but not sure about this season/year
As I said above, there will be some big sportscar drivers competing today, some F1 folks, but I dont think any NASCAR guys this year
Nascar's Bubba Wallace drove in a Supra yesterday for the Pilot Challenge 3 hour race (maybe it's 2.5 or 3.5, whatever), but that's the only nascar guy there this weekend. He didnt do great. Turns out running into someone is bad, got a flat tire and that set them back a lap.