I have an AT&T RM 877 (909 in device info) that I did the two step upgrade, first to 10166, that carried my settings over, I then did a factory reset with no sync, I then updated to the latest build, 10512. I then did another factory reset. Lumia Camera was gone after both upgrades, but returned after the factory both resets with no sync. I waited to add any info except my MS login for the insider app. until last.
I took a couple of pictures and it saves them both in JPG except one is large and one is much smaller. Is the larger called RAW? They both were JPG's according to the file type in the properties?
Just learning with the 1020 camera, glad it came back, pretty much got the phone for the camera. I haven't tried any of the other camera apps mentioned above. We'll see if the final W10 has it and go from there.