Here are two MX Player Pro clones running as floating windows and playing a video simultaneously. I’m using an app called Taskbar to start the clones (otherwise the home screen would hide the apps) but this isn’t using the Android 7.0 free-form window mode.
To make this work I had to change a couple of MX Player options. I disabled ‘Play alone’ and enabled ‘Background play’. VLC crashes unfortunately…
I also tried this on Android 4.3 where it generally works but touching anywhere outside a floating window immediately closes the app and MX Player also stops playback as soon the other window is selected.
It’s still pretty cool. To be continued…
App Cloner 