RealFeel isn't required for the mod, but IMO it's a nice addition. But I can't give you any recommended settings as I'm not an expert myself.
About setting up the cars (you meant the cars, right? Not the mod itself?), remember those are heavy cars with a sh*tton of power and even more torque. I personally set my cars up kind of understeery, as you can try to get the car to steer by using the throttle. However, as I set my McLaren M8F up for the Riverside race (which I managed to win), I set the car up for a grippy front and a loose rear, as I wanted to be able to go through the corners as well as possible and therefore I liked power-oversteer more. (I can share my Riverside setups if you want to have an example)