There is some dispute on how many meetings one person can schedule AND have running concurrently. We have had one user schedule more than 10 concurrent meetings but only 4 of them could be running at one time. Once the 5th meeting URL as clicked on they receive an error that says you're already hosting meetings, you need to close one of them first. In a separate community conversation about this topic another users said they could get 12 active meetings simultaneously. You may want to test this before you commit to providing that many rooms to be active at the same time. As far as I know there is no way to automatically start meetings using a CLI.
An alternative way to manage this would be to use breakout rooms. You should be able to have 100 breakout rooms in a meeting with up to 100 attendees in each room. Currently you would have to assign each user to the appropriate room but this can be done fairly easily if you have the attendee list and breakout room requests.
