Korean unification

How difficult would it be to integrate North and South Korea? Would it be as abrupt as East and West Germany?

it would probably completely fuck south koreas economy and the north would remain an utter shithole for decades onward.
not that china would ever let them reunite.

What if a second Korean War were to only push the border upwards, north of Pyongyang, still leaving a small buffer state between china?

It would be much harder and more expensive, so much so that South Korea would probably prefer not to unify at all.

>second korean war
literally n e v e r e v e r

I want to see a conventional war fought in the 21st century, that isn't in the Middle East

it would be extremely difficult, german reunification cost something like 2 to 3 trillion euros - and that was annex east germany whose standards of living were lightyears ahead of north korea's and their people far more educated and healthy. other user is right, it would totally fuck south korea's economy right up and might even collapse it barring a colossal amount of foreign aid.

china might go for it under some real particular circumstances, like all US and foreign troops off the korean peninsula, but is unlikely they'd greenlight it either.

autism. such a scenario would be all or nothing, china wouldn't be to interested in having a buffer rump state leftover as they'd look weak for letting it happen, the allies (SK+USA+whoever else) wouldn't stop short of the yalu river once the guns started going off.

What is the chance of it turning into a hot war with China ?

Between who? North Korea and China? It would go down in history as one of the shortest and most one-sided conflicts ever.