"Weight" is a calculated force that acts against movement of the wheel in any direction. It seeks to simulate the masses that would exist in the steering system of a real-world car. Consequently the optimal value will differ from car to car. Ideally, you want just enough "Weight" applied that you can steer with a fingertip down a long straight but not so much that you can hands-off completely.
"Torque" is the value you adjust in concert with iRacing's Force settings and ideally should not be set at values that cause over-exertion.
In iRacing (or any other sim), the "Telemetry" tab is your friend for identifying clipping. FFB sessions in excess of 60 seconds are displayed in real-time with the last 4 sessions stored as historical data.
The basic principle is to run a representative lap with "Torque" set to a comfortable level. 8-10Nm is a good starting point. Use the auto setting in iRacing to get into the Max Force ballpark and run another representative lap.
Check the "Telemetry" tab for clipping in the current session. If your clipping % is higher than 0.00%, raise the Nm value to reduce the gain from the sim and raise the "Torque" value to compensate.
Ensure the FFB session is ended by disabling FFB within iRacing then re-enabling it.
Iteratively run representative laps till "Telemetry" shows 0.00% clipping
Adjust the "Weight" if required to reflect the current settings
Finally switch to the "Settings" tab and reduce the "Controller Mode" iteratively until you feel no additional benefit (the lower your "Weight" values, the lower you can run Mode values without motor noise).