Most likely, yes. If you open the Event Viewer in Windows and go to the System section, you'll probably find you had an Nvidia driver crash which then recovered. Undervolts can be a little tricky in terms of stability and also be stable in one game and not in another. Just creep the voltage up by a single step at the same clock speed and go again. If you end up getting another random crash at some point, bump it up one more step. Rinse and repeat until you've gone weeks/months without any problems and you're likely fully stable. Personally, I'd also reboot as standard after a driver crash as it will frequently continue to behave in a funky way even if it "recovered" from it. And if all that sounds like too much of a faff, just increase the voltage back up in bigger increments.
That's been my experience too. Motherboards and PSUs can be the thing emitting coil whine, but changing one has never affected coil whine actually coming from a graphics card for me. Nor has it ever gone away over time. Hell, I've bought cards used that've had a whole lifetime of use before I got my hands on them and they still had coil whine (terribly so in some cases, like an R9 Fury I once owned). I had to send my 3080 FE back after spending so much time trying to get one as the noise was just insufferable.
I know some people also say that a degree of coil whine is inevitable, but I've had cards without it. That includes the 4070 Ti Super (Asus TUF model) that I'm currently using. It has absolutely none, even with the case open and my ear next to the card. It's wonderful.