I think this decision depends on the original scene.
If the brightest part was on Z-VII and you wished to reproduce it naturally in the print, then N-0 development seems to be called for. If you want the bright parts of the scene to be brighter than the original, then N+X is needed. I don't like constantly quoting AA, but he describes making this decision for Clearing Winter Storm.
So, if the scene contained say, clouds, you might want to brighten them and give N+X, but if it were say, a weathered wooden fence, there would be no natural ZVIII areas and Z-0 would seem to be right. In both cases, it would be an aesthetic, rather than a technical decision.
The modest intricacies of the Zone System can sometimes allow us to forget that it was designed with the final print in mind. All our decisions are servants of the print.
Visualisation (or for some authors, pre-visuaiisation) is the process whereby the photographer imagines the final print at the time of taking and makes exposure and development decisions with that in mind. Quite often, we have enough trouble with composition, the wind and dropping the cable release and may skip this stage. And inevitably, we may change our minds later.
I'm pretty sure that I know much less about scanning, but I've found that if the scan fits reasonably within the histogram, I can usually get a satisfactory print. All other things being equal, it seems remarkably easy to move a slider a couple of millimetres. With the proviso that I'm a very simple-minded scanner, the greatest danger seems to be a neg with too much density. In the darkroom, almost any density can be printed with a longer exposure, but a scanner seems to simply give up.
The AA book, Examples: The Making of 40 Photographs is good source of of information on how he made his photographic decisions, together with pleasant anecdotes of the relevant trip.
