Sometimes I think about all game rules and supplements in terms of prosthetics. Broadly speaking, a prosthetic is an artifact to replace a missing body part or remediate some deficiency. Some prosthetics are useful to almost everybody sometimes (stepladder) while some remediate a common deficit (glasses) and others are highly idiosyncratic. Similarly, the tasks referees and players need help with when playing a roleplaying game are various. Some seemingly common prosthetics include procedural systems to resolve fictional violence and guidelines to come up with fictional people having inner lives with some degree of complexity (such as non-player characters). Or how to decide how much fire a wizard can conjure.
So how does one decide what aspects of a game deserve elaboration and which can be left for the imagination of the players? What counts as design that punts where it should run? There is an essentially relativist objection to general standards for what deserves elaboration. It is hard to get beyond this subjective hurdle to make truly general recommendations without doing extensive observational research that people have not so far seemed interested in or resourced to do, especially for tabletop roleplaying games specifically.
For example, I have a low tolerance for certain kinds of hassle in rules, so I designed a lot of my mechanics as a prosthetic for that. Who knows what proportion of players are happy to track coin weight encumbrance exactly with spreadsheets or whatever? And might even enjoy it? I suspect that proportion is lower than players for whom slot based encumbrance would be more functional, but I lack the data, and I doubt anyone has much evidence relevant to this question beyond common sense platitudes and personal anecdotes.