You mean registrar. The registry is the place that administers the register of domains within a TLD (like .se or .mobi) and for some reason doesn’t let you order domains unless you want to become a registrar first

I don’t know which registry is the best but I can tell you about the worst. My registrar was also not amused by the mess that is AFNIC (twice now, concerning different domain names, and I don’t have many domains so if I already had multiple problems…). They sit in Paris and operate the TLDs of former colonies

For registrars, I picked OVH because they’re among the cheapest and their servers have been very reliable and fast across the months where I tested them before switching over. Their software is ass though, the forms frequently display three languages due to broken translations (their source language is French, my contract language is Dutch so a lot of elements are in Dutch, and then English trickles through where I guess they have a translation available but not to Dutch), multi-year ordering broke at some point and hasn’t gotten fixed, automatic renewal is wonky to set up… but once it runs, it simply works well so I still recommend it for people who want good service on a budget. You can also set records by editing the zone file which I appreciate. I’ve had registrars before that wouldn’t let you use certain record types; don’t have such problems here