Is there a more efficient way for me to make a map with modular pieces?

Hello! I currently have textures that I put on a plane then copy and paste the plane around so it all fits and whatnot, be it for walls, floor or ceiling, and I was wondering if there is a more organized and/or efficient way for me to build my map with these things rather than making a mess in the hierarchy and having thousand of planes? I had the idea for using a big plane and tiling the texture to fit but the problem is that if I need a plane smaller than that one I have to make a copy of the texture, if not multiple, to fit with different sized planes.

Is there something that maybe works like the array modifier or instance duplication in blender?

you can create a model in blender, make a prefab out of it in unity and then make a snap script that will spawn and position it properly in world space.

Have a look at pro builder, it’s free in Unity 2018.
I don’t know if you can make super high-rez photo realistic maps with it, but you’re currently using planes for all your level geometry. So Pro Builder should be well adapted to your needs.