Does north korea have actually good military power? I’ve seen their parades here and there, but does anyone know if they have updated equipment, trained military personnel, good intelligence, etc?

Military is the only thing they have. It might not be the most modern, but they have more artilery shells than any other country. Other stockpiles are huge AF as well. Almost 4% of their population are in active military service and 2% more are reservists. In terms of head count, they have almost as many active personel as Russia while having a fraction of population. Plenty of disposable meat!

Agreed that they have a pretty big military in terms of raw numbers. I’m not going to discuss quality because the biggest question mark here is force projection.

How are they planning on sending over any significant manpower and supplies across 2800km?

They don’t even have a navy capable of circumnavigating the korean peninsula, much less make the trip to Ukraine or the wrong side of Russia.

They have 2 transport aircraft, the bigger of the 2 has a max passenger capacity of 44 pax. Neither of those have the range to get near Ukraine when flying fully fueled, nevermind if it were fully loaded.