We know that a nation with 2.5 billion at least can get all three of the new fields (Capital, Leader, Religion); look at my nation to see.
There's also another nation in my region who has all three, and is just over 2 billion.
There's also another at 1.266 billion who has all three.
There's another in my region with only the capital city, at 1.265 billion
Then there's another with only a leader, with a population of 895 million.
There's another with only the capital city, at 668 million.
In conclusion, join my region.
Enough joking; looks like you can be a nation barely over 1 billion and still get all three; you either will receive the issues shortly, or have already gotten some and picked the wrong options.