Long story short, I don’t find UE4 a great tool for making complete maps.
I find it clunky, the workflow seems rather slow.
I’m wondering what software I can use to develop a map to be later finished and completed on UE4 (mostly from a polishing/gameplay/scripts perspective).
I’m talking only about the achitectural part of the game.
Build your walls, ceilings, door frames etc in a 3D modeling app of your preference, like Maya or Blender. Import them into your project in UE4 and build your level. That’s how it’s usually done. Check out the Reflection demo for instance.
You just need to work with some level of precision in your modeling apps. Use the correct scales, set the correct pivot points (origins) to your meshes and use the grid snapping function in UE to quickly build your levels.
How big your meshes are depends on your workflow and the type of game you’re working on. You could definitely create entire rooms in a single mesh. Well, at least the static parts. The reason why lots of people tend to create smaller elements is to be able to reuse modular level parts. You’ll just have to experiment what works best for you.