There is no limit for input buffer in the original mod - probably 2x stack size or 2x ingredient amount, whichever is higher. Effectively it is -1 (you can use -1 in my fork to revert to vanilla behaviour).
Craft-n-before-switch did not exist in the original mod, whenever the signal is lost/stop being the highest count, the combinator will change recipe. So effectively in original mod it is 0.
That being said, "Craft until zero" is a vanilla setting, it prevents combinator from changing recipe even when a signal isn't the highest, until the signal becomes 0.
