It depends on how strictly you take your role as captain/kaleun. In real life they did have a seperate person to do this navigation/plotting stuf. But imho, if this was automated then the game went boring for me real soon. Or there wasn't any freedom in the way it was done. I absolutely love SH3 for allowing a complete set of drawing tools on the map. (ok, still miss the ability to rename marks
) Sh2 got close, but wasn't really practical in use iirc.
Updates on is too accurate, and almost god-like situational awareness. No updates means all the work is for you to be done. I take the latter and try to find ways to minimise the amount of work I need to do. Match their speed as best as possible so you can take long intervals between plotting and you don't get too close too quickly. And don't plot each and every unit in a convoy, just the ones on the nearest corner.