MAX_SITE_POP_NUMBER
In my experience the game largely ignores this one(consider that all default civs have it set at 120, but in all site types the actual number often goes way above this). As far as I can tell the total amount of critters that can exist in a given site is currently hard coded as of right now.
I found this bug report on the tracker :
http://www.bay12games.com/dwarves/mantisbt/view.php?id=7547With comments from cephalo that is implying that all those worldgen and raws control are only actually controlling the historical figures, not the non historical ones (all those bunches of non named "goblins" by example) and that's the source of the problem when you try to keep population number under control.
Hmm, that could explain why whatever i enter as number to obtain low population, i'm still seeing goblin population in dark fortress still skyrocketing, because we have no way to control the real population of a civ, only the historical figure one.
But even so, with my experiment to keep civs population under a playable state, dwarves, elves and humans population number seems to work to my expectations according to my settings changes, it's the goblins that are the real problem (making the areas around dark fortress unplayable in adventure mode) with thousand of populations in dark fortresses.
So there's probably some hardcoded multiplier for dark fortress pop we can't do anything about.