I have it set so that homeless Sims will not move into houses. I have the marriage percentages set very low (less than 5%) and same with the pregnancy settings. Only opposite sex couples can get physically pregnant, and adoption only happens 1% for straight couples and something more like 15% for same-sex couples.
I saw someone else mentioned that in order to help with population control, they set it so that only married couples have babies. This wasn't out of some moral idea but it meant that they had to first pass through the "marriage" check and then another check for pregnancy, which exponentially cut down.
So far, the balance feels about right the way I have my settings but I will try adding that last one if it grows out of hand.
Do you all just sometimes delete some Sims when it starts to get too huge? That should be possible in "Other Households" tab, right? Any problems with doing that?