I suggest you avoid NordVPN since it has serious security issues. By default it does not block network traffic when the connection to their server is dropped which leads to leak of your traffic. It can be turned on but the issue is that it is not default. Also in default, it does not change your DNS servers, which has the similar issue as above. Thus in default settings, it is as insecure as if you were not using any VPN at all (since you cannot forsee the connection drops to their servers). Second, even if you change the settings, there is no guarantee that this will stay so, updates or you yourself can delete the configuration without realizing what you have done and then go on browsing thinking that your security is tight but it is not. Any security product that is provided with such lax default configuration is a bad product. Lastly, they could not explain the protocol difference or how to determine what protocol is used when connecting to their servers as opposed to other solutions which also provide network traffic blocking and dns by default.
To update based on the request from the developper. Your customer support effectively said that you do not care what the default settings are since users can change it, again, this is the problem in itself. And again, you claim a secure privacy oriented product, this has to reflect also in its default settings. Without kill switch on, any vpn for security and privacy purposes is almost completely useless, the same goes for DNS.