My layout can be seen above. I use:
Rstudio Theme: Modern
Editor Theme: Cobalt
Zoom: 150% (on a ~24" screen @ 4k)
Font: InputMono Light / 10
In the past, I have used a second screen in portrait mode for the console, but my desk does not have the room. Keeping it and the editor separate is advantageous.
Pop-out frames can be great too, especially for plots.