With all of our aircraft, we recommend using linear sensitivity curves for all axes as these are the sensitivities that the aircraft was developed using: https://support.justflight.com/en/support/solutions/articles/17000140463-optimal-controller-sensitivity-settings
We have received some reports from FS Realistic users, that the Prop Wash effect is causing steering issues in the Tomahawk. If you are using FS Realistic, try to disable the Prop Wash effect and see if that improves your experience.
The GPS option getting stuck on the EFB is a known issue in the marketplace version of the PA-38 Tomahawk, and a new build with a fix is currently being processed by the marketplace team. The update should be available on the next marketplace update cycle.
Mark - Just Flight