The registrar and the TLD have to be something trusted, I know people have gotten their cheap domains hijacked. Porkbun seems like a fair and inexpensive option, maybe with the .net TLD? Cheaper options exist but I don't want anything weird sounding that could trigger spam filters.
Also the naming scheme? I thought of firstname@lastname.tld, but many of them are taken, and if I were to set up multiple email aliases, I would be revealing my last name even if I don't want to. It should be at least a little professional sounding, something I won't regret in the long-term.
Of course many of these things are a matter of personal preference, but I want to hear how it works for everyone.
Naming scheme doesn't matter. Use whatever works for you.
Registrar is up to you. Namecheap is another popular option.
What is more important is you use the correct SPF, DMARC, and DKIM records. Your email host will tell you what the values should be (sans DMARC, but that's an easy search away).
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