Control of a cooling (thermo) fan is available through the Thermo fan dialog.
PWM fan output is not available for MEGA2560 MCU. Only on/off mode.
PWM. Set this to
Off if fan output is not used.
No for this setting, but if you have a fan circuit that flips the output, the polarity can be reversed with this setting
Speeduino fan output is control signal only. Not capable of driving fan motor directly. So relay is required to turn fan on and off or separate fan controller in case of PWM fan.
PWM Fan Curve sets the fan duty based on engine coolant temp. Duty range is 0-100%, but note that depending on the fan controller, the duty range can be different. In example 10-90% or the fan controller will go to fault state. See the fan controller specifications for the valid range.