“How we live determines how many live.”
Currently each one kilometre block of land can support 100 people. Not just for food and medicine but clothes and building materials as well. Only knowledge and seeds and people travelling need to be moved. With the reforestation and habitation of the deserts, there's been plenty of land for people to move to. So the issue of overpopulation hasn't been an issue.
Because there's no authority, each village is responsible for itself. Most villages are completely vegan and can support 120 people easily. If seems likely that 200 people per village is possible, but is it the right thing to do. Other villages are working towards converting the land for crops into forest farms and limiting their population to 100 people. Whatever happens, once all the land is under habitation the question of population is going to have to be addressed.
The obvious solution is to only have children when someone dies. Having this controlled will be a step in the wrong direction, but having it in mind might just be the solution. Once all the land is in use and everyone knows all the land is in use then our collective consciousness will change us into having fewer children. How this will manifest is unknown. Maybe more people won't want to have children or maybe more people will be gay. It's impossible to say. Maybe women will become fertile for a short time each year or at a later age and menopause might happen younger. Maybe all of these things will happen at the same or at different times one after the other or maybe something unforeseen.
Ultimately the answer is to be aware but to do nothing. Just let nature take its course. Already the average birth rate around the world has dropped considerably just by having faith in the future and knowing that when one gets older and needs care, the village will provide for everything.