Try this first
- Open ChromeOS settings -> go to Device section
- For the specific input device (mouse, trackpad) toggle off the "Enable mouse acceleration" or "Enable trackpad acceleration"
If you do not see the above settings, enable the option through Chrome flags and then re-try the above steps:
- Go to chrome://flags
- Scroll down to "Allow disabling mouse acceleration" and set to "Enabled"
- Reboot the Chromebook and see if it improves your mouse performance