In my experience Open Camera is even worse than the stock app. If you want better quality you need a Google camera port, but these are of questionable legality and come from unknown sources, so they pose a considerable security risk. I installed one anyway because I couldn’t stand the photos the stock app takes (if it saves the photo at all, at least in earlier versions it often didn’t). I posted a small comparison using the FP3+ camera and a Google Camera port vs. the stock app a while ago. Just three shots, each time first with Google Camera, then with the stock app.