Borrowing the image made by grenka, here is my idea on how pcam capture-UI could look like:
1. place ISO and shutter on two sides and use swipe gesture instead of slider which means swipe up or down on them would increase or decrease the value above.
2. Bottom placement for the manual focus, the thumb can easily reach this area when phone in landscape.
3. Each item on top acts as a switcher, tap to change to the another or there could be a drop-down menu like in default camera app.



4. the capturing part will auto-hide while user configure settings and slides in 0,5-1s after user lift his/her finger from the screen.


There could be some illogical parts in this but hope you find something useful from this for your app