There are several ways to connect the camera and the Android app each with it's own problems.
But first you should describe how the app will be used in more detail.
Will it be a designated unit or a mobile phone?
Will you start the app manually or do you want the app to start when the car is in reverse, under a speed limit etc?
Connection can be either in AP or ST mode.
Image can be jpeg or consecutive jpeg for http: or mjpg for rtsp: with current example projects.
As for now I'm only aware of 3 base examples, original software , CameraWebServer and micro-rtsp.
Android IDE with the esp32 plugin has a example "CameraWebServer" that sends settings back to the camera by a web interface.
Although not sure why you would like to send the settings as they should be hard coded.
As for the Android end an app is not really needed as it can all be done in a browser which might explain that you have not found much in the way of examples.
So basically you open a app with a browser plugin
You could look at some security camera apps or open a app with a Vlc-plugin but then you would probably have to use micro-rtsp.
Using Vlc would also make it easy to do the overlay.
This would be good as a project but it can not be used as a parking aid as you would probably not get below 0.5 seconds in delay.
It might be possible to go below that if you rewrite the code to send the picture in raw format if wifi bandwidth allows it.