Every team has someone who commits a broken test mesh straight into the Content folder. Unreal has a private sandbox for your experimental clutter away from version control. Just have to toggle this setting.
Hooking Substance directly into Unreal gives you live procedural control over wear and roughness right inside the viewport. Here is how to wire them up.
You won't learn believable environmental storytelling from copying ArtStation trends. The strongest level designer came from architecture, geography, and urban planning. Here are books that show you how those spaces are organized.