If Russia nuclear strikes Ukraine, would the West really follow up with nuclear counter strikes?

No, that’s not what would occur. NATO and the US would utterly destroy Russia’s military capabilities using conventional means, though. And perhaps even occupy Moscow temporarily.

However, what China would do is another matter. That I don’t have a lot of insight on but I can guarantee it would not be nothing. Most likely it would occupy significant parts of eastern Russia and Siberia, I’d guess. But that I’m less clear on.