https://fivethirtyeight.com/features/what-powerlifting-tells...
If you want watch people go all out with AAS, HGH, insulin and all that you can watch modern bodybuilding.
Edit: See here for a really detailed comparison from someone who knows what he's talking about: https://www.strongerbyscience.com/steroids-and-strength-diff...
As per motor sport it is obvious what class a car is in, there is no pretending to be the other class.
The testing would be more part of signing up to a given class, everyone would know what everyone was taking whether that be nothing or everything. Much like how in Motorsport you know cylinder count, oil used and so on.
It would be both a sport and a laboratory for transhumanism. I'd be incredibly interested to see what science came out of it.
There are probably ethical arguments to be made against doing that, but... meh.