I deleted all of the the townies and I manage their spawn by using a combination of MCCC, NPCC and a mod that keeps sims in their homeworlds for most part. I currently have 104 sims, the only premade npc I keep is the father winter, the rest are my playable sims (currently about 45 households) and npcs created by me which I put in homes together based on the world they live in. The game uses them as needed for the npc jobs, or I change their job through NPCC myself. With the current settings I have in MCCC an NPCC the game creates only one additional sim which I delete at the end of each gaming session. Currently my other households look like this. I will add the npcs to all worlds, but currently I only created them for the worlds I play most often.
https://64.media.tumblr.com/06e1d1a66e868e2e152f95a8087f32fa/0c0dd7f254cbd897-c3/s500x750/e7703aca36af4121b005dad0dff0312fe9349b9e.png