Here's the issue with war, and the fact that Holla Forums knows absolutely zero regarding modern Chinese strategy;
What is promised is a blank cheque. It means nothing in the big picture. Taking NK down as SK will crumble the SK economy harder than the DDR hit SRG after the fall of the Berlin wall. Taking NK down as China will hit the economy and flood refugees. Taking NK down as USA is a no-no because it is a threat to China's national security due to the borders and potential of tanks near Beijing. It just won't happen, let it go.
NK has had more than 60 years to perfectly aim every missile, artillery piece, you name it, they aimed it, at South Korean cities like Seoul.
No matter how many special forces, bombers, drones, ect that China, South Korea, and America throw, there isn't a way they could neutralise all weapons before Seoul and similar are flattened. Millions of civilian casualities, massive economic damage, it is simply too risky and the weight of South Korean cities and civilians rest on those soldiers.
There is a very real possiblity that some day, Kim will be disposed of. His purges make him difficult to coup, but there is a very real possibility of him being disposed of with help of the CPC due to closer relations, but not currently as his brother was recently killed.
If USA goes to war with China, Russia wins. And neither side wants that.
Even if it came to war, the cost would be massive considering the DF anti-ship/carrier missiles can cripple or outright sink aircraft carriers (the backbone of naval and American military strength) in Guam with one missile.
The most reasonable result is China will eventually assume control of NK, and the UN will hardly bat an eye.
The only issue I can't fathom is just how loyal the NK special forces are. The US handled the dismantlement of Saddam's special forces wasn't great, and many Muslim terror groups have Saddam's former elite soldiers as their leaders and advisors.
NK has easily twice as many extremely loyal troops as Saddam had at his prime.