The biggest changes to help the cars are the diff settings and the dampers.
Watch your replays. The old replays used to have wheel hop that looked like a broken shock absorber. That doesn't happen anymore. However, the defaults seem to be about 5 clicks too low.
I'm using the Merc 190 Evo again as I keep tweaking it. I like to use Watkins Glen and Dragon Tail because you have to use the curbs for a good lap. Those curbs will tell you all you need to know about your suspension set up. The Mercedes is one of the few street cars that, when upgraded, can take GR3/GR4 level of suspension settings.
Here, the springs are in the low 3 range, the compression is 30, and the expansion 50. Note how settled it is after the bus stop. It still isn't perfect, but it's usable.