Works for (almost) all cases IMHO. You can drop your last name if there is a slight relationship or less formal. And I just drop down to -[first name] after the relationship is there and for ongoing conversation/threads. "Cheers" is nice but don't think it hits as well in US.
American here, similar style, I just use 'Thanks' instead of Best. They're similar in just being short and kind and impersonal. I think both are about perfect. Anything less seems unprofessional, anything more sticks out like a sore thumb.
Usually just my first name unless it's formal and introductory, as my email will come from First Last as the sender already.
Cheers is fine in the US I think, but I at least assume the speaker is British or Aussie. If I know they're American, it comes across a little pretentious or inauthentic IMO...same as when Americans say 'the states.' Makes me roll my eyes but not like day ruining or relationship affecting.
"Thanks in advance" is generally considered bad etiquette as it is directive and, really doesn't add anything. It's just nicer all round to thank in reply.
Kind of similar to how I think of best but thanks is to preemptive if there is no ask so I add it in main message when there is something that was completed.
Honestly I would find "Best," confusing, and I don't think I've ever seen it before.
What is it supposed to mean? "All the best"? "Best wishes"? Why not just say that?
Depending on the rest of the content I would probably assume either that someone was going for one of the above and didn't even notice that they a word, or that the author is a non-native speaker translating something from their primary language.
Yes, I think it's supposed to be sort for "best wishes" or "best regards". It's part of a trend in email correspondence where people seem to think that typing an extra few letters will cost them too much time (which of course is money). The same way you get people typing "pls" and "tks" in emails.
[full name]
Works for (almost) all cases IMHO. You can drop your last name if there is a slight relationship or less formal. And I just drop down to -[first name] after the relationship is there and for ongoing conversation/threads. "Cheers" is nice but don't think it hits as well in US.