Trying to come to grips with open wheel

[Terminus Est]

I've pretty much exclusively stuck to various tin-top cars up until this point, so I decided to branch out and try the Formula Abarth for Assetto Corsa. I did pretty well at Monza and after a while was turning in consistent 1:39-1:40 lap times, so I decided to try a modern F3 track...and got a brutal crash course in how downforce works as I understeered into tire walls over and over.

Everything about this car (and the RSR Formula 3 car, which is similar but a bit more extreme) is counterintuitive. Fast sweepers that are utterly terrifying in a closed wheel car are a piece of cake in this car, while tight hairpins I can just roll right through in an an old 911 or a Group A M3 are frustrating understeer-fests where I can never find a comfortable line. Coasting doesn't work like it does in larger cars because there's not enough weight in either the car itself or the flywheel so it loses RPMs too quickly. It is easy to drive fast and difficult to drive slow. Even braking doesn't work the way one would expect, as they become progressively less effective as you decelerate. Is there a babby's first open wheel guide for "normal" car drivers to help me make sense of these vehicles?