>>212020110 (OP)2 billion is too much. But 420 millions would be just the perfect number.
If i could get two wishes. Id wish Brazil a population in the early 400 millions.
And to racemix to exist but in waaay less degree, and more modern than traditional. Like, having 200 million blacks, 200 million whites, 20 million mixed race people. And your 2 million natives, 3 million Japanese, 5 million triracial. Just fine.
Anything more than that, like a billion, stops being an advantage and is a liability. The USA could bear 1 billion Americans though.