China is a question but I'd say that noone is benefiting from WW3 apart from perhaps military industry. So I don't really believe China will be too happy because they have a lot going on internally and they don't really need aditional problems that RUS will inevitably cause them.
But as I said: I really hope that time will prove me wrong.
What do you mean? If nuclear escalation happens and WW3 is triggered there is absolutely no world for the military industry to benefit from. Weapons will be required, of course, so production will continue but there would be no semblance of economy or governments as we know them now.
Nukes flying are world-ending, at least the human world and societies we currently experience. There's no profit to be made in total global mayhem.
WW3 does not necessarily mean nukes at all. I personally think - based on how Russian generals used the military funding to enrich themselves - that most of the Russian nukes are not operational. They might have some low-yield "tactical" nukes (something like nuclear grenades). And I seriously doubt that US would use theirs since as soon as you use nukes, everyone will and after that there is no winner anymore.
Unless you calculate you can be the last man standing in a world with drastically reduced pressure on natural resources due to depopulation
Even if it stays that way - Russia against the West - and even if on paper Russia will lose since they are alone - nukes can fly especially over Europe. I'd understand why someone would call that a World War.
There is also a formality in the definition of war vs "special operation". When Russia formally declares war against Ukraine, the West will be considered a cobelligerent if they supply Ukraine with weapons. The partial mobilization is a step towards that