Hi think this is possible but not sure so if someone could point me in the right direction that would be greatly appreciated. I want pi hole on raspberry pi to block all ads on all devices connected to it and for it to also connect them to a VPN using pia(is it possible for certain devices to connect to servers in different countries). Basically just how to add a VPN to all devices using the same pi running pi hole. I just want it on the home network no accessing pi hole externally. Thanks
You usually don't want to use a Pi as a router or internet gateway because its networking hardware isn't very fast. You should instead setup a VPN connection via your router (if it supports it).
Theoretically, a Pi can handle 100 Mbps. However, in practice you are very unlikely to see anything close to that. Google will tell you more accurate stats on how much network traffic the Pi can handle in different situations.