DNS server of a delegated domain to a master host, how to transfer it correctly?

Question

Domain Name System

In general, in connection with the problem at the masterhost, the question of moving has come to a head.
I read that it would be better to have separate dns hosting and file hosting.
The domain is delegated to the master host.
there are backups.
And there are questions:
1. which dns hosting to choose for primary dns
2. similarly for secondary
3. how to overwrite them? Do I need to somehow untie it from the masterhost? Or do you still need to get a key to transfer domains?
Primary I so understand is a registrar?
I'm sure I missed something important, if so, tell me.

PS the hosting on which the site files will be located, of course, I will also change))

Answer 1

I can not imagine a clear reason in which the word "separately" sounds. Type fault tolerance if only.
And so - there is no difference - where and what will lie - if it works as it should, stably and everything suits in terms of price, functionality, etc.
If by problems with the master host you mean some technical problems, but file hosting (apparently that's what you call just hosting) remains with them - even if dns is available elsewhere, your site will be unavailable.

Answer 2

At your choice. Everything is very easy and simple.
1. DNS-hostings: Cloudflare, Yandex Connect
2. Just register the DNS-hosting ns-server at the registrar
I didn't understand what "Primary registrar" means.