@raschemmel post #1. The circuit is part of an IOT application where the power consumption is crucial. After some research I came to the above solution to switch all unused components off while the Atmega328P is in deep sleep (1 + 2). The LED was meant as an example of a consumer, in reality this would be at least an HC-12 433 MHz HF module and one or more sensors which together will probably use 1 A max (3).
I'm not a pro and every constructive input is welcome.
@ReverseEMF thanks for the addition. It'll take me some time to process your information as I'm obviously not a pro.
@6v6gt thanks, I've ordered some NDP6020P.