Roughly speaking FSM + stack based approaches are perfectly fine for 100 entities, but not for 1k. Once you get to that point you can still make it work but it

Roughly speaking FSM + stack based approaches are perfectly fine for 100 entities, but not for 1k. Once you get to that point you can still make it work but it will take a lot of work to make it as fast as possible, whereas you'd have been better served by more branchless approaches that doesn't parse/jump the FSM.