You already have put quite a lot of thought into this and it definitely is an interesting question. However, I don't think it is answerable as stricly as you might hope, but I don't think that's a bad thing actually. Your computations aren't that far off, though.
You already realized that figure scale in LEGO is a strange beast due to the rather weird proportions of LEGO figures. So when using specific Modular Buildings for reference, you already have a problem with the minifig version not being entirely accurate to reality. Add to this the fact that storey heights can also vary significantly in reality. Trying to pin that to an accurate scale might get rather difficult. That BrickArchitect article is a good start, though, and a rough approximation that I tend to go by for figure scale is indeed 1:42, which is also conveniently about half of H0 scale (1:87), as known from the model train world.
But then you also have the problem of abstraction. The Mini Modulars, albeit about a quarter in size of their bigger brothers, also might abstract some elements in order to get a better representation of the original's overall style less than its accurate dimensions. But if we go by quarter scale, we could say it's maybe around 1:175, which isn't that far off your 1:190. That would also mean a human would be conventiently around 1cm tall, which is also roughly over 1 brick, whatever measurement you prefer. However, the exact number doesn't quite matter too much. What is more important, and the Mini Modulars demonstrate that too, is picking something that fits the pieces. For example using SNOTed 1x2 tiles as doors is a common technique. Also the premade 2x2 windows make for useful elements. So ~2 bricks for one storey isn't a bad idea, which would also match with your results.
For some more practical examples, I have seen a few YouTube cities using an approach inspired by the Mini Modular style, too, and working with 8x8 modules. This conveniently fits to the LEGO grid of 32x32 basplates and the like. It also has other advantages, like simple 2-lane roads being 6 wide with 1 stud sidewalk on each side, which in turn fits a road built sideways and made up of 7 plates per lane with a neat 1 plate striping in the middle. This can then conveniently host 2-wide cars, or the "CITY Advent Calender scale" ;-). For people they tend to use either nanofigs (what BrickLink calls "trophy figures") or builing something about 4 plates high, which also fits to the scale not too badly.
Afterall, even the Micropolis standard isn't as strict as everything always adhering to 1:285. You can really put anything between 1:250 and 1:300 into a Micropolis layout and maybe even more. It just has to fit the overall aesthetics and be reasonable to build. You don't want to build cars that are 1.25 or 0.75 studs wide, you want to put a tile onto a jumper and have an iconic and recognizeable micro car. I haven't worked too much in Micropolis myself, but I made the experience that you shouldn't pain yourself too much with thinking if that fence should be one plate higher or lower rather than if the overall look fits and it's practical to build. In fact I've even seen houses in the scale of the Mini Modulars put into a Micropolis layout (she even uses her own micro versions of LEGO Modular Building sets) and although they can look a bit big if you try to compute the exact scale, I think it works very well in the overall layout.
I personally also try to compute an actual scale for at least my Architecture models that try to get real-world proportions as close as possible, but even there it's not always easy to compute that to an exact number based on abstractions that the LEGO system requires. You might have to build it higher than it is wide or you might have to build that window smaller than it really is. And with something like a freely designed micro city, it's more important you have a solid idea how to build roads, cars, doors, and whatever in a convenient way and everything fits well together.
So on the bottom line, have a rough scale in mind, but don't get hung up on the exact number. In fact, what's more practical is having various numbers in mind, for each of the different use-cases, and then pick whatever fits to what you're building. I.e. establish a reasonable standard for major elements that works well together and that you're comfortable with. If people are then actually 1:175, cars 1:150 and trains 1:200 doesn't matter all too much because noone will actually do those computations as long as you got a coherent model. The ideas for how to build it from the pieces you got will then come with some experience in the scale. Some easy guidelines for Mini Modular scale (which also fit to what you came up with) would probably be:
2-brick storeys, 1-brick people, 2-stud cars, 1.5x Micropolis, 1/4 figure scale, or anything between 1:150 and 1:200.