But you have to keep it up all the time I would imagine and things happen. Not sure what happens if you4 location changes.
I don’t understand your question. I personally configured our VPN service to my WiFi router, so all my and my wife’s devices are behind a VPN when connected by WiFi.
If you are using public WiFi you can install a VPN app from your VPN provider on your phone or laptop and run it while connected to public WiFi.
People can set up a fake access point from their laptop. When you connect to it to get free internet service they can see everything you are doing, including typing usernames and passwords. If you are behind a VPN you are safe even if you are connected to a fake access point because everything you do is encrypted.
Most decent paid VPNs have a feature that locks the internet down (called a "kill switch") if you lose connection to your VPN so you don't have leaks. It doesn't happen often (losing VPN connection), but when it does it is a pain for mine budget VPN because I have to restart my computer to re-up everything. Maybe once a month.