Level design
Powerd by Unreal Engine
The quick brown fox jumps over the lazy dog
The Level design is a very important step to make your world believable.
A lot of development studios have an individual "Style".
to find your own style, its important to know what kind of style you feel most comfort.
Models and placement
To get a good feeling where and what is placed in your map, its a good way to look up your setup in a real world environment or other resources like movies or other games.
Take good care of your details in the world and try to fit the necessary objects in your world.
Textures
Texture size is with the current graphic card technologies no longer a big deal, nevertheless keep in mind that 4k multi channel Textures get up to 150 mb, so your project can get very fast very huge in size. A good way is to find a middle way that fits your recommendations to the players.
Performance
Yes, the new engine promises the best renderings and amazing shadows in real time. But the truth is, those projects are mostly highly optimized and target high end PCs. Its very important to learn the optimizations for the engine.