2.8 duramax diesel "smoke limits

What exactly does the smoke limits do in the diesel maps? Does it have the final say or is it controlling a different parameter from the main table completely?

Im fitting some +30 injector nozzles and just trying to decide how to control the off boost/ cruse and idle fueling

The smoke limit table or tables have the final say in the pulse width to be supplied to the injectors. As such, you need to be mindful of making sure that they aren't artificially limiting the amount of fuel you can supply in a modified calibration.