I have woohooer set for Risky at 10% chance and TFB set at 15%. So pregnancies don't happen often. However, I'm wondering if my town residents (Non Played ones) will follow the same chance or will the game just make sims pregnant regardless of the woohoo settings?

Woohooer will follow the same settings on all sims in town, but it only pushes its effects on sims who are animated and can't really do so on those who have gone into semi-hibernation mode in their own houses. SP is the one that impregnates sims without any on-screen actions taking place and it will do so if it "thinks" more pregnancies need to form in your town to keep the population in balance or if it thinks couples are not being fulfilled by getting their wishes to have as many kids as they may want as per SP's settings and their traits.

I've had SP get carried away a bit at times and have even had it complain to me with on-screen messages that the mod can't find anyone to impregnate (the eligible sims are already pregnant or are in a cooldown period apparently) so I should do something about that. With babies already coming out of my town's proverbial ears at the points I've seen this happen, I tend to laugh that off and set the Population cap lower so that there shouldn't be anymore pregnancies unless I dictate them or say so anyway, and then things generally calm down for a while.

Thanks, that's good to know