Do production bonuses affect gold production? I know there was something about that they don't work together so I just wanted to see if it changed or if it was ever the case?
Anything that increases the goods produced does work on gold. Production efficiency has no effect though.
This right here. So for example, a constable doesn't affect gold, but a workshop does.
Yes, and the last building that gives 50% (?) more is probably worth the useless ones you need to build first.