How can I record the screen and the rear camera on an iPhone simultaneously?
In the absence of an app that allows overlaying screen recording and a rear camera recording simultaneously (odd why the app makers didn't provide an option to select the rear camera instead of just the front facing camera), here is a workaround I found.


Record the screen recording using the iOS screen recorder
Record the rear camera video using the iOS camera app
Download iMovie from the App Store and overlay the two recordings together (split, picture in picture etc).


Here is a video tutorial I found on YouTube which explains how to combine/overlay two recordings/videos using iMovie on iOS.

https://www.youtube.com/watch?v=D_qx75zTjr0

I'm not marking this as the answer as this is not my ideal scenario, it would have been nice to have an app do it, but it's a workaround for now.