“Affect Translucent Lighting” on the light just prevents their injection, there’s still come constant cost from clearing and filtering the volume.
You can disable it with the console command ‘r.TranslucentLightingVolume 0’, or lower the resolution with ‘r.TranslucencyLightingVolumeDim 32’. These can be overridden in your game’s DefaultEngine.ini (SystemSettings section) to apply them on load.
Props to you for using profilegpu to narrow down the costs.