There is no official anwser, and i honestly don't think people should expect a press conference to lay out the details and strategies of China in concern of SK to go nuclear. That is not to say that Chinese media and internet is not flooded with discussions, in fact there are way too much opinions and the quality of those are also varying greatly.
But if we stay at present, only THAAD is being deployed and the Chinese concern is mostly because the longrange sensors are capable to spying far into the mainland, the missile system itself is not that much of an issue. There are a lot of conflicting interests involved, but i think anything about concrete strategy/countermeaseaur/whatever from China will depend on if SK is indeed commiting in arming itself with nukes. Befor those evidence are seen there will be mostly only conplaining and pub talk in the public.
I get that there won't be any official or possibly unofficial statement.
My question wasn't about SK going nuclear, it was about SK developing the conventional capabilities to fight a nuclear armed North Korea. Those conventional capabilities will be much more effective against China than the current Army-focused development. Would that affect China's position towards DPRK nuclear weapons?