Please also make sure you only use on of the pet related packages: either nonewpetstrays or nohiddenpetstrays. Only install one version of the unimportantsims package. The mod comes with several modules so you can temporarily get rid of modules if you feel you need more Sims of a certain kind.
The only Sims that will be generated are those with special traits or careers required. The mod also reduces the generation of new townies significantly. With this mod, celebrities will no longer invade all lots in your neighbourhoods.
However, you will need to use the move objects on cheat to place them inside.