Is it possible to limit total number of units for AI player so they don't clutter the whole map with unit spamming? This also keeps AI from bankrupting.
At first I misunderstood the question,
You cannot limit the AI unit count in a traditional way. You can however reduce the difficulty of the game, which does affect the unit count.
Other then that,
Mods like these can make you start with a current number of units, get free units at certain times and its also possible to limit units with mods.