Many options, conflicting information
This is a big problem. I have just finished telling the Qubes developers that they need to make an official guide or package a solution themselves https://www.mail-archive.com/qubes-devel@googlegroups.com/msg05567.html
If you want the best leak protection then you have to use Configuring a ProxyVM VPN Gateway - #58 by qubesfirewallbug
It doesn’t matter that you don’t understand nftables, just follow the guide and it will work.