In regards to the DNS advice should I use that for both my PC and android ? And when would I use a vpn?
You should setup your preferred DNS server everything really. On your phone, on your computer and on your router if you can. DNS is the absolute easiest way to track and block/hijack browsing habits, so hardcoding your devices to use a standard one like NextDNS, Quad9 or Cloud flare will put you very far ahead
Regarding VPNs, commercial VPNs are really overhyped, and thats because they’re a cash cow for operators. See Tom Scott’s video on the subject if you prefer this britishplained to you. All a VPN is is a tunnel from your device to the VPN server wherever that is, so you’ll look like your traffic is originating from that VPN server, plus all of your traffic is going to that VPN server so you have to trust that that server isn’t compromised nor slurping up all of the data to sell/provide security agencies. Clear text browsing traffic will also be secured between your device and the VPN server, but that’s super uncommon nowadays. Realistically a commercial VPN is best for if you’re doing illegal activities such as piracy because it will add layers of abstraction should a private company or public agency wish to investigate your activities and try to identify you. I do use Tailscale with an exit node on my home network when connecting to public wifi just in case the network is misconfigured, but it’s really just another layer of Swiss cheese security.