a) Please see `device/google/coral/rro_overlays/WifiOverlay/` for a sample overlay app.
b) The list of values that can be overlayed are listed in service/res/values/overlayable.xml.
c) OEMs can add the flags they want to override in res/values/config.xml of this sample app
and put the sample app in either system, product or vendor partition of the device.