On the S6, Camera FV5 worked really great. That was android 5. Android 6 seems to break a lot of stuff e.g. access to SD card (some apps can do it, some don't; I don't know why).
Interesting info about the Pro mode shortcut! Yes that really works. Many thanks for that.
However the button double-click still launches the default camera mode.
"Oversharpening and oversaturated processing are system wide. So no matter what apps you use to take picture, it will be oversharpening and oversaturated like stock app or even worse(unless you shoot raw with that apps ofc)."
I think this is what the camera API delivers and the camera app has no choice over it.
I have just tried another app, Camera Pro (Mr Mayer's), whose default mode delivers exactly the same photo as the S7 stock app. And if I de-sharpen and de-saturate using its controls, I get what I would call corrupted images, with nasty jpeg artefacts. And this is exactly what happens with Camera FV5!
But then all these camera apps are no more than just control panels for the camera API. These apps don't actually process the image, pixel by pixel. One of the developers told me this; he said it would be too slow otherwise for peoples' expectations. IOW, all the image adjustments are done by the OS. The camera app just provides the buttons
So I think Samsung either have a bug in the API (so these extra controls, namely the unsharp mask level, don't actually work) or they have changed the API so the apps no longer issue the right parameters.
Camera Pro was outstanding on the Nokia 808 which still totally beats the S6, S7, any Iphone... I got rid of it only because the browser options were all useless for some websites I needed to use. It's a pity that after all this time, 4 years, a £550 phone still doesn't come anywhere near the 808.
But I think an app which does RAW and reduces it to around 10MP (like Camera Pro did on the 808) would deliver a much more natural result than the stock S7 app. I have seen the RAW images and with suitable photoshopping they come out good. The stock app stores the RAWs into an obscure location in internal memory, but a 3rd party app which implements RAW and the downsampling could then write the finished one to the SD card.