When to use bcm2835-v4l2 on raspicam v2.1

Camera model Raspberry Pi Camera v2.1

What is the problem? Custom Image Preferences does not recognise the camera ("custom settings") unavailable. I also have the FOV issue others have reported which may or may not be because of sensor modes.

What did you already try to solve it? Fiddled with octopi.txt and /etc/modules to no end

Additional information about your setup (OctoPrint version, OctoPi version, ...) latest versions on all

So based on the sensor mode article it would appear I need to go for e.g. 1640x1232 to get my full FOV.

Except if I do that in octopi.txt I don't see any difference in the view I get. I suspect that this is because of the bcm2835-v4l2 driver which (I think?) emulates raspicam to look like a usb cam in order to enable Custom Image Preferences (is that correct btw?).

So my questions are

  1. Is my understanding of the role of bcm2835-v4l2 correct? (to make it look like USB only so that Custom Image Preferences can be enabled)
  2. Is it bcm2835-v4l2's fault if I can't get 'strange" resolutions like 1640x1232 to fire up? or am I barking up the wrong tree here? In which case I'd rather ditch the Custom Image Preference in favour for a better resolution
  3. Despite using bcm2835-v4l2 and all settings exactly as prescribed in this guide, I still don't see the raspicam recognised in the Custom Image Preferences dialog in octoprint. Is this normal for the V2.1? (not that it matters, but then, I am a bit OCD)