What do domain NS records affect?

Question

Domain Name System

I explain. I have a domain from one registrar and hosting for this domain from another company. For the correct operation of the domain, the hoster gave me a dns address, which I registered in the administration panel at my registrar. Type 120.20.20.20. Ok, done. Everything is working. But the hoster still offers to change the registrar's NS records to their own (delegation). I now have ns1.myregistrator.com, ns2.... on ns1.myhost.ru
Well, how is the delegation going. Is this delegation essential? What does it give? What is the difference between DNS, which I changed at the beginning, and NS, which may be different? My registrar says that ns-servers are just so cool: DDoS protection, reliable, etc.
Everywhere they write that you need to delegate the domain to the hoster, but they don’t write why and why exactly the hoster needs a delegation.

Answer 1

Domain NS records must point to the DNS server that will be responsible for this domain.
It is on NS servers that all records about this domain are located - its MX records, A-records of its subdomains, and so on.
You can do whatever you like, it's a matter of convenience - through which control panel you want to manage your domain.

Answer 2

Offered for convenience. Everything will be in one place and most of the entries will be added correctly and automatically. Subdomains, mail, etc.

Answer 3

If you delegate to someone who provides you with support services for your DNS, then you do not have to do anything manually at the registrar.
Everything will be managed from the name server (DNS) service provider.
For me, it's so convenient. That's how I've done it.