Given it is very much to be mentioned how to set them in the most correct way on Fedora 28 instead of those of Google???

nmcli con mod TIM-24378841 ipv4.ignore-auto-dns yes
nmcli con mod TIM-24378841 ipv4.dns "8.8.8.8, 8.8.4.4"
nmcli con mod TIM-24378841 ipv6.ignore-auto-dns yes
nmcli con mod TIM-24378841 ipv6.dns "2001:4860:4860::8888, 2001:4860:4860::8844"

Quelli di Google li impostavo in quel modo,ma quelli di CloudFlare???

Set up DNS of CloudFlare

Not knowing the service I do not know all the parameters, I read only a few articles like the one mentioned...

Someone would know how to help me!!!!