Yay! Have fun!

You could check if

• you are editing the right ini file by changing another setting and see if it takes effect in the game
• something else like Mangohud is forcing vsync

If it you manage to turn of vsync and the mouse lag is gone you probably want to limit your frame rate to something close to your monitor refresh rate to minimize screen tearing. You could use Mangohud or libstrangle for that.

If you have vsync enabled, try disabling it and see if that helps with the input lag.