1. Have no rules. I usually switch between families when I get bored.
2. Don't keep track. There's a good mix between single sims and families. But my favourite is a couple of siblings (adults and teens, or two adults). It helps with social needs and it's less overwhelming to manage a household with just two sims.
3. Often switch between families multiple times per day.
4. Use all the world but my fav is San Myshuno. Love apartment living and i like the aesthetic better than all the other neighbourhood. Most of my main families live in San Myshuno.
5. None that I could think of.
6. I honestly don't know. I switch between how I play all the time. Sometimes I play families, sometime I try to be a completionist, and sometimes vampires. I have different families for different gameplay. I guess that's why I like switching between families so much.