If you’re tunneling all of your traffic through the VPN then it doesn’t matter which you use.
If you’re using policy routing to only send certain devices through it you probably want to set those devices to use a public DNS resolver, to avoid leaking your DNS lookups.
I’m with NordVPN and I starting having problems with my PfSense DNS resolver resolving from the root servers. As I’d just enabled PfBlockerNg I assumed it was my problem so backed my changes out until I was back to base yet still had the issue. I raised this on the PfSense forum and some smart people performed some tests which suggested that Nord is intercepting these DNS requests.
I’ve emailed Nord and the admit there is an issue with custom DNS addresses but have no eta on the fix. I asked if they intercepted the requests and they ignored that question and another on exactly what the issue is which makes me a bit worried. I’ve re-asked and waiting for a reply.
Networking is my weak area. I know the basics and can set things up but when it goes wrong it is clear I didn’t sacrifice enough small furry animals to dark gods when I was learning it.