I have majority of my domains with Porkbun.com
The rest are with Namecheap.com
Used to do a lot of business with GoDaddy, but they have become so obsessed with marketing a million other services on the way to checkout, that it finally turned me off. I like clean interfaces that allow me to just focus on my domains.
Not really as a domain needs to point to a specific server by the use of Nameservers. (normally 2). It is the nameservers that point to the servers IP addresses.
You can have 1 million domains that all point to the same server as a domain is not a different name for an IP address. If this is what you think then you are in the wrong business and need to learn alot before to continue as a web host.
Enom, ResellerClub, NameCheap, and NameSilo are all great resellers that we've used at various stages.
These days, because we're not reselling domains and instead using them just for ourselves, Google Domains is our registrar of choice. Not only do you get an easy admin interface, but you get the nameservers on Google Cloud network, so the response time is even faster for lookups.