I currently consider Small map size, Quick game speed as the game's standard settings. Normal map size, Standard speed feels to me like a Large map with slow speed. With the building of districts on the map, it seems like they are representational, rather than literal, depictions of the world, which I think suits a smaller board-game style map with a quicker game pace. The increased need for thinking, regarding city-planning and District placement, uses up a lot of brain resources, so I prefer not to have too many cities. More than a dozen feels like too many to have to deal with. The maximum number of civs allowed in the vanilla game on small size is 10, which seems like a good number. Civs average at half a dozen or so cities, although some civs can get much higher. I maintain the default 2:3 ratio of civs to city-states, so I think 15 city-states is also a good number, and more than this would be too much. I do increase number of religions, though (to 6 on Small map and 8 on Standard map).