One point: We're not actually overpopulated. I'm not really sure why the media likes to propagate that myth. The conspiracy part of my brain has it's hypotheses.
The entire human population could actually fit in suburbs cover an area the size of Spain. Spain isn't a small country by any means, but that's also suburbs, which are evil incarnate. We also could fit in a small number of very large cities.
The main problem is feeding everybody...which isn't really a problem...it's only annoying because it's not cheap. The current way we feed everyone is planting a single crop on a large space of land, then using machinery to harvest it.
We have robots now. That's not an issue anymore. We can now start planting multiple crops, in forests if we want, using hydroponics, growing far more food for the amount of land.
We actually already grow more food than the world needs. The reason some starve is due to greed and waste and shortages in particular areas. But we could easily increase our population several times it's current size without any real issues. Food might increase in price...but it's already insanely priced in many areas, mainly just due to greed.
Can we fit there while living comfortably? Dunno though. Overpopulation is real here, at least in my country.
No one lives comfortably in suburbs. They're hell. It's much better when you live closer to people that aren't horrible nasty people, which everyone turns into in suburbs. They're just little boxes segregating everyone into their own little tiny area. It's better when you have your own little tiny area for some things, but have to actually interact and get along with people most of the time.
Most overpopulation is actually a problem of poor design. We all live in tiny boxes in various places. We're segregated into living areas for sound and pollution reasons...but that also means that when we have to go to anywhere, the traffic to that area is insane.
You gotta split up common places people would go into small little satellite locations. Little restaurants in resident areas. Some residents in commercial areas. There are people that go to school and study how to do it properly to ensure there arean't these problems. And once you stop being super cheap and insisting everything go back to ground level, it makes it a lot easier.