I have my Sims 4 on two platforms. My PC is older, so it just has the base game, and a couple stuff packs that became free for a short time, as well as some mods/cc stuff. Another platform is on the PS4, which I own almost everything on, but missing most new packs, and almost all the kits.
For my PC Sims 4, I have a lot of save files, with one family or more for each file. Some files just have a single family, and eventually their descendants. While others may have one big family, and smaller families mixed in. My biggest family on my PC version is up to about 20 played Sims. My smallest single family is made up of 4 Sims. The other save files are usually between 5-18 Sims so far.
My PS4 is a different animal. I have a lot of save files, and each save file starts at the minimum of 20 to over 100. Most of them are slightly themed, and I have fun creating different versions of the same Sims, and moving them all into the same world as well. Most are still in 1st to 2nd generations, and starting to pair them up for the 3rd generation. Planning to reduce the population, since I have so many Sims. I plan to get Sims 4: For Rent to help with the population. My plans for the 3rd generation is to marry the families together, move some of the spares to the supernatural side, and turn aging back on to age my Sims. Or just keep aging up, and grow up my 1st generation sims.