What makes North Korea dangerous is the large amount of artillery, troops and armor they possess.
The DMZ is gonna be one hell of a hot place if North Korea ever decides to cross the border in force. They’ll be raining down artillery well ahead of their advance. They’ll have saboteurs and special forces running amok behind South Korean lines. Lots of mayhem and lots of civilian casualties too.
I certainly hope that the Air Force (and the ROK Air Force) can slow the North Korean advance long enough to allow our (and the ROK) troops to get into position.
The front line troops have to fight a holding action or staged withdrawal in the face of superior forces. However, the attackers aren't going to get much further than they can go on one tank of fuel. Then with their restricted mobility and depleted ammunition stocks we would counter attack and execute maneuver warfare - attacking when and where we decided, with initiative and surprise.
What makes this problematic in Korea is that Seoul is only what, 40 miles south of the 38th parallel? Not a lot of room to trade for time.