Tap-testing thread mills does a great job of determining the best speed. Because of their low or no helix geometry thread mills are highly prone to chatter if you pick the wrong speed. The axial depth of cut and the radial depth are determined by the application and the thread mill program.
The depth of cut and width of cut are pre-determined by the program, but you can determine the best speeds. Tap-test just as you would an endmill.
Set the current conditions (where the Dashboard opens) to the prescribed width and depth of cut.
The cutting geometry is typically pretty negative, so follow the manufacturer's recommendations for feed rate. If you get chatter, increase the number of passes to reduce the radial engagement.