de0u Thanks for your thorough information. It is definitely eye-opening and I appreciate you taking the time to elaborate on it. The only reason why I use the Gcam is because of the different modes they have. I really wish Graphene cam has more modes, but alas, CameraX doesn't have it yet for Pixel phone. The Google Photos is simply for convenience to preview the photos you took from GCam and to quickly edit them. All in all, it's just for convenience.
I checked out Privacy Guides for most of the FOSS I use, if not all. And so far, I dont see any recommendations for Camera (I personally have no issue with the Gallery app from Graphene). So, if you have any recommendation for a camera app, more than happy to try that out :)
Again thanks a lot for your time.