Overpopulation is a thing in biology for when a given animal population is too great for a specific environments carrying capacity. Thing is that this is a theoretical thing that is based on animal behavior and the environment being held static. Now this can be a thing for more simple organisms, but humans can both adapt their behavior as well as their environment so it really doesnt apply. Also the concept of overpopulation in this sense is also dubious because it is usually applied in cases where an environment has been destabilized some way to remove natural checks on population which can lead to rapid abnormal growth and then crashes (See Link below). So yeah overpopulation is a thing best left for theoretical models and not applied to questions on how we want to structure our society.

https://en.wikipedia.org/wiki/St._Matthew_Island