How many families per world

Depends on age of save. In the old days tried plying TS2 style with multiple families per world, which lead to utter chaos at best. Currently only 1 or 2 worlds - occasionally 3 - is active for living in with 1 or sometimes 2 families in primary world, 1 in any secondary ones. That provides variety and cuts down on the chaos. Some saves are 1 sim in 1 world. Regardless of how many sims are active there is usually a lot of tinkering with premades and key townies.