Thanks for response.
NRDP is not for XI only. I currently have this NRDP approach implemented across my nagioscore 4 instances. Nagios core 3 to Nagioscore 4 should work also.
I haven’t have successful nagioscore3/4->livestatus->check-mk-raw-1.6.0p16 experience yet. I will keep exploring. check-mk-raw looks like a good solution to ease our nagioscore infra support burden.