Adjustable floor like The Sims

I’m working on a tycoon like, TopDown game where you build your own gym. I managed to follow trough 3ProngGaming’s tutorial until episode 20 so I actually know how to place buildings but I’m sure that I might need another way of handling the floors in order to reduce lag and optimize the game and I have no clue about how to do it.

I’m looking for something like as in The Sims: The Sims floor placing

The easiest way would be to use HISM components.