The Cortex M3 used in the Nano does not have a DAC and so we’re limited to a PWM square wave for the output signal. Power consumption will be negligible when not loaded. Setting duty cycle to zero will disable PWM and ground the output. If you like to keep if off by default, you can save this configuration as part of your power on profile and then use quick select to set duty cycle to 50%.
The link below has more information on the constraints related to sampling speed. 1 Ms/s is the upper limit with the current design.