Open an example level and you’ll see. You can easily tell what was made in Unreal because it will most likely be a primitive (cube, sphere, etc. There was a point back in UDK where you could single that stuff out but I’m unsure as to how it works now). But you’ll see that, aside from maybe a completely flat floor or wall, EVERYTHING else is created outside of Unreal. What you get when you create inside of Unreal was what used to be called a ‘Cubic Level’ (because most things wind up being made out of cubes). This usually looks cheap and un-professional unless you’ve got some serious logic behind why you’re doing it that way. I guess if you’re making something for mobile that needs to look that way (like a retro looking game) it could work. But generally it’s better to make your own assets in an outside program.