I have experimented a lot now, my current power settings are as follows:
M5.Power.setPowerBoostOnOff(false); //Change the power on / off method. The power does not turn off when connected via USB. true=Press and hold to turn on / off. false=Turn on / off with two short presses.
M5.Power.setPowerBoostSet(true); //Change the power on / off method true=ON / OFF in one short press. false=same as above
M5.Power.setPowerVin(true); //When the power supply from USB etc. is cut off, Decide whether to turn on the power again.
M5.Power.setPowerBtnEn(true); //Set whether to accept the power button.
M5.Power.setPowerBoostKeepOn(false); //Always output power. True= Always output power. False=not Always output power.
M5.Power.setAutoBootOnLoad(true); //Set whether to automatically start when power consumption occurs
This lets me turn the M5 off/on with the power button with single click. However, it does NOT work if the USB HOST module is connected.
I can turn it off, but it never turns on again, until I connect usb to the M5core directly.