Unity can work perfectly at 100 Hz with a small performance penalty. It may even run at 500 or 1000 Hz, but then the application requires a powerful machine to run.
Physics frequency is configured as Project Settings > Time > Fixed Timestep. Default value is 0.02 (50 Hz). Set to 0.01 for 100 Hz.
I haven't configured go karts yet, but VPP has all the components required. Surely they can be simulated to some realistic extent.
Currently there are no plans to include a go kart example in VPP, but I could create it on demand as a separately paid service. Check out the rates and conditions here:
https://vehiclephysics.com/about/support/#professional-services
If you're interested, please contact me by email to further discuss this matter. Thank you!