One thing that may help is that much of the world of architecture (good architecture that is...) now and in the past is based on the "golden section" and other natural geometries.

Further, the "Asian Foot" (be it Japanese, Korean, Chinese etc) is very similar (~98%) the same as the imperial foot...give or take a "millimetre" here or there...and that is the "next hint!"
There foot is not based on units of "12" but units of "10" (or 8ths in some regions) As such switching to metric was easy for them and that is the scale today use often and/or there work translates into much easier. I have worked in metric for so many decades now I could never go back. That alone may assist you in getting a better handle on all this.

I would also share, in many istances, (especially folk styles) "tape measures" and other related "measuring tools" are often either "self created" and/or not really used...

I didn't touch a tape measure for the first ten years of working wood, but "scale" based on the geometry and design of what I was trying to create or emulate using "story pole," template and "line layout" modalities...

Let us know if we can do more...

Regards,

j