PiVPN + Pi-Hole installation let crashes the Raspberry

Okay, then you shouldn't do this. The two options are:

  1. Route all traffic through the VPN
    This may be slow as all traffic will be routed through the VPN. However, it will be safe even if the WiFi connection during your holidays is insecure.

  2. Route only DNS traffic through VPN
    This may be significantly faster than the first option. However, there will be little to no added security through insecure connections.