It's the whole package.
Main metering timing is (somewhat) controlled by your HSAB and your emulsion bleeds. The requirements are obviously different for every booster....
This is how the Autolite carbs got away with not having much of an idle circuit, they tried to do all the metering with the annular boosters.
Finding exactly when the idle circuit becomes inactive and when the main comes online requires either an o2 or causing a lean surge and then backtracking as needed.
Once you get a pretty decent calibration down it works pretty well with *almost* any engine (especially as a baseline). Downlegs don't change things around too much, annulars mess it all up and you need to do a lot of work to get the calibration to work.
Yeah, it takes a good bit of driving around, tuning, changing, but once you have it, it works. Keep good notes.