Yes, the built in screen recorder works great most of the time and yes ... the files are gigantic.Finally, someone who understood the same as me!
To answer your question, I could just quote my previous reply, but I’ll just say: the system’s (iOS, iPadOS, macOS) recording tool, can both record the screen AND external/internal audio. If you disable the mic for the recording, then you’ll capture the video AND the audio.
The only downside is that resulting files, especially on macs with Retina display, can end up being pretty big, but nothing that HandBrake can’t solve.