A little question here about interior design

So, you guys know a good way to design rooms?
Usually, I use BSP Brushes and convert it to static meshes, but it end up looking to “blocky”.
The other way I thought is, using an external software (such as Cinema 4D, Maya, Blender…), then exporting it to UE4 via Datasmith.

There are tons of assets in the Epic Market place for that, many of them are free. Have you looked there?