Were I to "get serious" about making pictures with the iPhone, there are number of apps which, when installed, appropriate the iPhone's native camera software and replace it with their own. These apps allow for incredible control over many picture making options. Options such as allowing for RAW capture, control over ISO, focus, shutter speed and so on. In effect and actual practice, the apps turn the iPhone camera module into a picture making tool which closely resembles and rivals an entry level digital camera with manual controls.
Then, of course, there are iPhone processing apps which allow for near desktop software level contol - converting and processing RAW files, highlight, shadow, tonal / contast, WB and noise reduction capabilities. There is even one processing app which allows for identifying and changing / deleting individual processing steps at any time without effecting any other processing steps. AND, the finished file can be saved with those processing steps intact for changes at any time in the future!
In any event, I am trying to resist most of these advanced capability apps. While I have acquired a few, I am endevoring to keep my snapshot picture making as simple as possible in order to keep within the snapshot picture making paradigm ... aka: you press the button, we do the rest.