Actually, you can find out which settings are used by the game. Add bLODPopActors to both [Display] and [LOD] and go into the game. Open the console (~) and use the GetINISetting "setting:section" commands:
getini "bLODPopActors:Display" getini "bLODPopActors:LOD"
You should see "INISetting bLODPopActors:Display >> Not Found" since the game doesn't read this setting from the Display section even if you manually add it to the Display section.
The second command should show "INISetting bLODPopActors >> 0" where 0 is the actual value you've set in the LOD section.