So the boon of using geometry for level design goes a lot deeper when you aren’t using simple shapes like this, however there is one big instance of use here:
You grab all of the walls, maybe even the floor. Then in the details window, if they’re all geometry, you get the option of combining them all into one static mesh, reducing draws significantly. Select the centermost piece last, as this will be the anchor.
Of course you can use carving, bezels, negative pieces (they remove geometry, so you could easily make things like holes or doors.
Check out this video, it’s not long and you’ll likely learn some really good uses for your project:
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