Google Maps has picture-in-picture mode
I only noticed this morning that if you press the Home button when Google Maps is navigating, it will drop to a PiP overlay on top of any other app. A quick press on it will do a temporary zoom, a press and hold will allow you to move it around, and a double click opens it full screen again.
Here I have it running it over Waze so I compare route directions. Yes I could do sit screen as well but Waze is not well optimised for split screen.