I would suspect that some countries would definitely go to China due to the more sizable economy. But a large number of others - especially those with more democratic idealogies - would go with the Euro.

China would absolutely not want to have a reserve currency. Their export economy would be destroyed overnight.

Doesn't China currently address this by having two currencies, with one dedicated to offshore use?

China only has one currency, the renminbi or yuan. There are capital controls so it isn't fully traded on international markets. It has only been internationally traded since 2015, and I think there were various schemes before that.

Aren't CNY and CNH effectively two different currencies, despite having the same name and being somewhat linked?

I hadn't noticed that. I guess that is how they manage the capital controls. It sounds like they are supposed to be the same internally but that there is a spread. That seems like it could be a weakness.

Perhaps? I can't imagine that either could take the loss of production capacity the way the US has. The global inflation of product prices alone is staggering to consider.

The RMB is a terrible reserve currency since the CCP can just arbitrarily change its value by decree.

Sure — but if the CCP decided it wanted the benefits of owning a reserve currency, it could change that. Then suddenly it looks more attractive.