LED Strip power supply switch
You should better consider a high side switch since the WS2812B is more than a passive component and could be damaged if input signals persist while GND is switched OFF.
VSS will go near to VDD over time and Vi is only allowed to be VSS - 0.5 V to VDD + 0.5 V. The IC could be damaged if Vi left this interval.

A flyback diode or snubber network is only required for loads with decent inductivity which is not the case here.

The capacitor should better be connected to ground permanently to be able to stabilise VDD from the beginning.