Lighting is very simple. It’s only a Skylight and a Directional Light.
No .ini file is being tweaked. I’m not using light portals either (I should to reduce build times but this is a simple scene).
In terms of parameters Static Lighting Level Scale is low around 0.1, Num Indirect Lighting Bounces at max, Indirect lighting quality at 8-10, and indirect lighting smoothness at 1.
Post processing is mostly color grading. Look into Epic’s documentation on that (LUTs). They completely change the mood of your scene.
I read into a lot of Koola’s threads and the Lightmass thread in this forum; those helped a lot.
Most important though is composition. Understanding space, form, light, shadows, etc. Look at how famous architects like Tadao Ando and or Louis Khan form their space with light and shadow. Light and shadow define your space more so than the walls.