[LG V20 ROMs, Kernels, Recoveries, & Other Developm] x86cpu:
Close, it's not exactly how overlays work (and I wasn't even sure until I started poking at the code). You can only overlay things that a "pre-defined", ie... from here: https://github.com/LineageOS/android_packages_apps_Snap/blob/cm-14.1/res/values/config.xml Which no shutter speed or values exist. But in therory you can overlay any .xml file, it just has to match the name and path in the overlay folder. (config.xml to config.xml), it'll change it, won't add, just overlay that new value on top. :( From here: https://github.com/LineageOS/android_packages_apps_Snap/blob/cm-14.1/res/values/cm_strings.xml there is a default of "0", which is supposed to be auto.

<!-- Shutter speed -->
<string name="pref_camera_shutter_speed_title">Shutter speed</string>
<string name="pref_camera_shutter_speed_default" translatable="false">0</string>

<string name="pref_camera_shutter_speed_entry_0" translatable="false">0</string>
<string name="pref_camera_shutter_speed_entry_1_6000" translatable="false">1/6000</string>
<string name="pref_camera_shutter_speed_entry_1_4000" translatable="false">1/4000</string>
<string name="pref_camera_shutter_speed_entry_1_2000" translatable="false">1/2000</string>
<string name="pref_camera_shutter_speed_entry_1_1000" translatable="false">1/1000</string>
<string name="pref_camera_shutter_speed_entry_1_500" translatable="false">1/500</string>
<string name="pref_camera_shutter_speed_entry_1_250" translatable="false">1/250</string>
<string name="pref_camera_shutter_speed_entry_1_125" translatable="false">1/125</string>
<string name="pref_camera_shutter_speed_entry_1_60" translatable="false">1/60</string>
<string name="pref_camera_shutter_speed_entry_1_30" translatable="false">1/30</string>
<string name="pref_camera_shutter_speed_entry_1_15" translatable="false">1/25</string>
<string name="pref_camera_shutter_speed_entry_1_8" translatable="false">1/8</string>
<string name="pref_camera_shutter_speed_entry_1_4" translatable="false">1/4</string>
<string name="pref_camera_shutter_speed_entry_1_2" translatable="false">1/2</string>
<string name="pref_camera_shutter_speed_entry_1" translatable="false">1</string>
<string name="pref_camera_shutter_speed_entry_2" translatable="false">2</string>
<string name="pref_camera_shutter_speed_entry_4" translatable="false">4</string>
<string name="pref_camera_shutter_speed_entry_8" translatable="false">8</string>
<string name="pref_camera_shutter_speed_entry_15" translatable="false">15</string>
<string name="pref_camera_shutter_speed_entry_30" translatable="false">30</string>

However, there are some LG parameters in the config.xml which might help to disable or change the LG/camera behavior. The 1st one does not appear to be set, so not sure it that would do anything or not, but some things to try.

<!-- Set's parameter "lge-camera" for LGE devices. -->
<bool name="lge_camera">false</bool>

<!-- Set's manufacturer specific parameters on startup.
Example: lge-camera=1;cam-mode=0 -->
<string name="manufacturer_key_values"></string>

<!-- Enable support for LGE HDR -->
<bool name="lge_hdr_mode">false</bool>

There is an abolute issue with white-balance, no matter what camera. Even opencamera, etc.. any of them, if you change the white-balance off "auto", it is black, completly dark and not working at all. These are handleded by some proprietary-files, which I have validate are pulled from the us996 device, and it still fails. So... some other minor proprietary file missing? ... maybe... something to look into again.. Thanks.