elfprince You shouldn't generalize like that. Many different VPN setups have very different configurations. Some work with just usernames + passwords, some with usernames + passwords + client certificate auth, and some with just client certificate auth.
The setup that @sortedsand talks about is pretty common with business VPNs, and is how my company's is configured as well. The client certificate is needed for mutual TLS with the VPN server and then once that connection is made the client sends username + password (in our case this is authenticated by a LDAP server).
@sortedsand I don't know much about the NetworkManager applets in Budgie desktop (which is the "widget" that integrates with the desktop to allow you to start/stop VPNs and whatnot), but I do know that if you launch nm-connection-editor you will get a much more powerful NetworkManager interface. If you then click the "+" at the bottom and scroll through the list there should be an option to "Import a saved VPN configuration" which might do what you want.