Sorry. I don't agree: if people can get near a print they will, regardless of size. With the exception of prints that are large precisely because they will be viewed from distance, like a billboard, people will tend to stand at about the same viewing distances. At countless exhibitions, gallery shows and auctions with prints from 10x8" to a couple of metres wide or larger, I have seen people getting as close as the ropes allow. And there are usually no ropes.
Sure, with a large print people might also step back back I see no signs of their not stepping close, too.
SO I think resolution and the print size of fine art print making go hand in hand and that there is a generally linear relationship between resolution and sensible print size. However, fat, well exposed pixels make better prints, ceteris paribus, than weedy, starved ones. So assuming good optics, I would make a larger print from a 20mp crop of an IQ180 than I would from an RX100 frame. I happily print 180dpi from the former but feel more comfortable well north of 200DPI for the latter.