Added and to laptop - can I change modem/router too?

So I changed DNS addresses to wifi on my laptop for IPv4 and it works fine

Can I now change for the R45 cable modem set up on my PC under the same protocol DNS since my PC is not wifi?

I hope I’ve stated this properly…

Sure, you can change your router, which would change DNS for any devices which are getting those settings dynamically. This is often the easiest way to change it for a large number of devices at once.

You can also explicitly set it for your devices. Windows (and most operating systems) maintains the DNS settings on a per connection basis. So you would make the same change for your EtherNet adapter in the network settings. I believe this article describes that pretty well (different IP addresses to enter obviously):

Either method works. I first did it on individual devices before making the change globally using my home router. Hope that helps!