I played almost exclusively deity on normal map sizes and a pure warmongerer strategy.
]With these settings, the usefull and productive core of my civ normally wasnt more than like 10 cities or so. Normally i made 1 circle around my capital with 8 cities or less (depending on the amount of unusable spaces in that circle) and only made 1 or 2 cities outside of that circle to get iron and other resources. Then i started my war. With that amount of cities, the settler factory never really was usefull. the time it takes to build a granary made it faster to build the cities without settler factory. (i know the settler factory also gives advantages later on, but my early war and conquest on neighbour is a multitude more important).