NEC 2070NX calibrate Native or sRGB?
In case of calibration software "native" means just measuring the current output of the monitor.
In case of the monitor menu I suppose "native" means no internal monitor adjustments.
If you set anything other than Native in the software your targets are achieved using videocard LUTs (in this particular case).
Both internal monitor adjustments and videocard LUT adjustments are potentially harmful to image quality (such as banding artifacts on a greyscale gradient). That's because they result in less than 256 values per channel. So it's often recommended to stick close to Native white point and gamma both in terms of software targets and internal monitor adjustments .
If you do want to calibrate your monitor to a defined white point target (6500K in your case) you have an option of choosing a preset close to your target, an option of adjusting RGB values in onscreen menu to that target and an option of leaving the monitor as it is. The rest will be done with videocard LUTs anyway, whichever way you go. Which way you do it depends on which one of them gives you less image quality artifacts.
Look at a fullscrean greyscale gradient. If it's smooth and neutral using your current settings there's no reason to try anything else.
|Chicago Alley by tko|
from Down the alleyway
|Callan-5680 by vbuhay|
from What Child's Dream May Come
|Widget by Wilfried HKG|
|Oxbow Bend by stickpointed|
from Landscape - Colour #2