What should I use as a "nameserver"?

So I went through my configs after updating, something I didn't do for a long time.
I noticed that the name server has the Google DNS 8.8.8.8 and 8.8.4.4
And I was like, "wow, maybe this is what slows down my Plex" (?). my main router is already set to that dns.

I removed it, and wasn't able to do stuff like
- update the Plex jail server.
- download subtitles through the app
- cloning git repos in the jail server.
- pinging 8.8.8.8 worked for some reason. didn't try pinging google.com...

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