Hi guys, I wanted to tell things like IRL. As a pilot it gets hard for me to express myself in DCS terms only, my mistake. Lets see.
True North = The lines that you follow parallel to the meridians which will get you to the north pole
Magnetic North = Is the "north" that you will reach if you follow the N in a compass. Since there is declination in the Earth, if you follow a compass all the way to the N you will reach a point very deviated to the actual north.
Grid North = The north that you trace on a map, a perfect straight vertical line on a map is the grid north, which will not be the same as the true north except for one point in the map that is called the center of the cartesian axis for a given projection.
So yes, as I learned today, you have to put whatever the ruler says in the PCN. But just in DCS, in the real m2000 you need to put true north which you will get by tracing the angle FROM the meridian that crosses your navigational point.
Cheers.