Workflow for overriding camera settings in view layers?

Hi all. I’ve been trying to wrap my head around how to create simple attribute overrides in blender per view layer - similar to render layer overrides in maya. I’ve read about libraries, linked scenes, ID data etc but I still can’t seem to get a clear idea of how I am supposed to achieve this.

I have a scene with a subject and a background. I am going to comp the subject over the background so I create two view layers, bty_foreground and bty_background. I can render these out and composite them. Fine…but in bty_background what I would like to do is adjust the camera Aperture to be different than the foreground element. I cannot seem to figure out how I am to accomplish this in blender. In maya I would simply right click the attribute and choose ‘create override’ and it would change for that layer. Can’t do that in blender…so what’s the trick?