When I worked as an SRE at Stack Overflow we used name.com for all our domains (and R53/GCP/Azure for DNS). Never had any issues, and worth adding to any short list you come up with.

If you do whois lookups against the top 50 websites you'll see a lot of them use a small set of registrar's. But not all of them accept small businesses.

Probably something similar to CSC Global.

Probably because you want enterprise grade support, a real person that you can call and will help you solve your problems without having to deal with low level support before.