Even the most populated countries like China, India, and others have already developed, and they are still creating other things that will make their citizens enjoy their way of leaving. To me, overpopulation cannot affect the development of a country if the government in such a country is doing well, but in a situation where the government is corrupt, they don’t care about their citizens.
You can see that even if there are resources available, they don’t care to make use of these resources in such a way that they create job opportunities for the citizens, and I believe job opportunities are one of the ways that we can say a country is developing when everybody is working. And that is what the Chinese government is still doing. With their very large population, are we going to say they did not develop? Nah, mate, so if a government uses available resources in a nation to create other ways of earning, there will be no poverty.
As per the international laws and criteria, both China and India are categorized as developing countries and aren't developed countries, although China's growth rate is way higher and it is more developed as a nation than India and there is also a difference in unemployment and literacy rate between the two countries. If we talk about population or overpopulation, it actually does make a difference when it comes to developing a country and providing the best services and amenities to the citizens.
A country with a popular of 63 Million people will be easier to manage and develop than a country with a population of 1.4 Billion. I know that natural resources and the abilities of the authorities to produce wealth and increase the GDP of the country matter in this but the population does have its effects.