I've done my testing back in April 2023, comparing my old system to my current. (Both stock)
Old System: Ryzen 2200g, 8GB 2666mhz, GTX 1060 6GB
Current System: Ryzen 5700X, 32GB 3200mhz, RTX 3070
With the old system, I was able to get a max of 30 cars (Both modded and kunos cars) on any track that supported big grids. I mainly tested 30 Porsche 911 GT3 Cups around Le Mans and it worked with no issues, maybe a bit of stuttering here and there, but nothing distracting from the overall experience. I've tried a bunch of Nvidia control panel stuff, Lowing graphics; which were already pretty low, but it made little to no difference. The only thing that I can recommend doing (If you want to) is to change your power option to 'High performance' in your windows control panel. This managed to squeeze a tiny bit more performance out of it, this usually works with low end stuff. I've tried it with the current PC, but there's no difference.
With the current system, I can run 80-85 cars easily at the full Nordschleife 108. The PC couldn't take much more when I put it at 90 cars lol, but I was (and still) super happy with the results. Now I can run full Daytona, Le Mans and even VLN/NLS grids with modded cars, HOWEVER...
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The Ai doesn't know how to take corners properly around this configuration and It ends up in a blood bath full of carnage at the following corners: Hohenrain, Flugplatz, Sometimes Adenauer Forest, etc. No matter how much you nerf the Ai in the menu, they'll find a way to screw up. If you want my honest opinion, upgrading your specs is the way to go about it.