However, I don't think WW3 will last very long. Our technology is such that even IF Putin was crazy enough to launch, drones plus a good nuclear defense shield would probably shoot down anything he sent up.
Won't last very long, true, but there is nothing positive with a nuclear war. If you live in North America, or Europe including Russia, you are dead.
Russia has the most nuclear warheads in the world. No country will ever launch only one nuclear missile on another nuclear power, that would be stupid. If Russia attacks the US or France, or UK, they will launch everything they have on those countries at once. All those nuclear warheads would obliterate those countries. The US would respond and obliterate Russia. I live in the NY area, so no chance of surviving, that would be one of the first targets.
If you live in Asia, or South American, or Africa or Australia or some island out there, you would probably be fine, but life would drastically change.