Where does the figure of 100 come from? I've effectively finished the game by converting all the heathens several times now with a population of around 90. Of course, when the heathens convert, the population will rise above the 90 limit for a while, but unless the older villagers are rejuvenated regularly the population will drop down to 90 or below again as they die. I say "effectively finished" because I've never yet completed a collection that would allow me a higher population cap.
I'll go along with 90, it's not that much of a difference! Still to many villagers to keep track of; in my opinion. in all previous VV games, one could get away with as little or as many villagers as one cared to. Not so in this one.