Over on Gothridge Manor I made a comment that I thought the 12 miles per hex that Kingmaker use is a too large for mapping a sandbox setting. Roger emailed me to ask me some more detail. So I am turning the answer into a post.
Writing sandbox settings can be painstaking work at time. Even writing tersely the quantity of locales can be overwhelming. My observation that you will have a dozen or so really good ideas and the rest you crib from whatever idea generator or random table you have.
You could limit this but you don't want to make the region so small that the player are able to move past it's bounds in a session or two. Nor you want to make the locale spaced so far apart that and the howling wilderness of the 30 mile hex effect.
I found that making your hexes between 3 to 6 miles to be ideal. If you are using 1/2" hexes on a 8.5 by 11 paper you get a region of 135 miles by 90 miles. It comes roughly to 27 hex columns and 19 hex rows. For that size three dozen locales fit nicely.
Expanded beyond that to the size of a Judges Guild Wilderlands detailing that many locales becomes a bit of chore. Good random tables help as an idea generator.
As for Kingmaker what they did was put something in just about every hex. However they choose to only detail a 6 hex column by 5 hex row region creating 24 locales of varying detail.