>They stand for Long Exposure Noise Reduction and >High ISO Noise Reduction respectively.
Long exposure noise reduction only kicks in for exposures longer than 30sec I think. It basically takes a 2nd exposure of the same length but with the shutter closed. This gathers noise data from the sensor which can be "subtracted" from the original exposure to eliminate noise caused by pixel variations (which have various causes).
High ISO noise reduction is a default Noise reduction that kicks in for ISO values above 1600 (iirc) even if you set NR to OFF. If shooting in bright light it is not necessary - and lengthens file write times - so turn it off if not needed
In bright light shooting conditions you will get high contrast so Active D lighting (aka ADL) may be a good idea but HINR and LENR and various other bad light settings can be disabled....and so on
I will try to compile a listing of my settings using the settings spreadsheet and post it here but I give no guarantee to its effectiveness. Not sure how to post a spreadsheet here - will try to find out.
If you want to figure it out for yourself then I suggest create a table in a spreadhseet or word processor with 6 columns. column 1 = list all the settings in Shooting Menu Bank Column 2 = make notes about how each one works - the manual provides limited info, you may find one of the specialist books on D800 useful. Column 3 = tick if useful for good light handheld - note preferred settings where a range is available Column 4 = tick if good for low light handheld........and notes Column 5 = tick if good for low light on support (tripod)...notes Column 6 = tick if good for (choose a purpose independent of the others above)
Similar table for Custom Setting Menu
Column 3 = A, Col 4 = B , Col 5 = C, Col 6 = D
You'll figure out a system that works for you - then enjoy testing and fine tuning it.