I think there's a backroom/blackmail deal that we destroy Russia and China gets Taiwan.

China comes out ahead in all scenarios. If we win totally against Russia, China's likely to get a more effective, less dangerous, easier to control trading partner out of it. If there's some nukes their main enemy U.S. will suffer a lot. Even if there's total war China isn't the main target and will withstand nuclear fallout way better than any other country.