I'm overawed by the length some go to to keep on top of their play. Well done!
I just start a family or single Sim in a home, give them some money, cooking skills etc. and a job and let them get on with it until I play them again. It's surprising what they get up to. After a Patch once some of them had even changed sex after getting adult but kept their female names!
I try to fill most houses with my Sims and have about 70 plus Sim families on the go in my current save so I forget what they were up to originally anyway. My current Save is UK suburban and English Tudor mostly.