KAL’s 321 sim has been delivered and assembled in their sim building but appears not yet to be in regular use unlike the 737Max sim.
As regards aircraft arrival, I’m not sure, but latest I heard was start of next year, but really not sure on this point (Perhaps continuing 737Max grounding may change this?) I’m guessing pay will be similar to 737 fleet. All of KAL’s airliner fleet have at least some expats apart from the 787 and A220 at present, I presume they and the 321s will have expats eventually, indeed the agencies have made tentative enquirees in the past to interest for transition to the new 321s.