Isn't there a problem with all these circuits?
You need to remember that if you disconnect the Vcc rail from the supply an Arduino's
pins will all be at ground, so they will pull a PNP or p-channel ON immediately.
And if you do low side switching the converse situation is true, all the Arduino pins are
at Vcc and will turn on any NPN or n-channel switch.
To get this sort of power switch you are best doing it with a CMOS flip-flop circuit, use
the button to switch on, and an Arduino pin to switch off.