The Chinese are a threat but they “fight” a different way — as you can see: they aren’t going the lengths Russia has in terms of outright military confrontation because they have more to lose economically.
Russia hasn’t made the same economic gains, and therefore has less to lose. Hence the geopolitical gambles they make on this scale and this level of recklessness.
And it was Russia that help North Korea get where it is militarily, not China.