Whose to say a Russia run correctly, i.e medicine researched, health care implemented, POPs wealthy, no huge costly wars, shouldn't be incredibly populous ? The reason AI Russia isn't so lucky is because it is more or less following the historically destructive path. War, overtaxing etc. Paradox compensated for this by giving them the highest Pop growth mod around. If you are worried about a human Russia, all you need to do is tweak this number to your liking.