I had 4 on a small map. I don't think it was working right as it said people were jobless and I could assign the job. There was a weird spotlight on the first capital as well. Overall I'm not sure how effective the AI is just yet, but it was nice seeing these cities come to life.
Viewing post in TMA RTS Tech Demo jam comments
Thought I fixed that but I guess the UI still gets confused when only AI players are in game, to remove the fog of war spotlight the game can be set to Sandbox game mode, in Default game mode the Capitals and Radar structures are used to reveal the map with a tech tree element to increase the range of revealed map, as well as how far you can zoom out.