Picture-in-picture will work with Netflix on Android 8.1
An example of what a Netflix video might look like using the Picture-in-Picture feature available with Android 8.1
Picture-in-picture is one of the most anticipated features of Android 8.0 (Oreo). With PiP, users can watch a video "floating" on the screen even while doing something else with their handset. They can also drag the video around to one of the screen's corners if they so desire. Currently available on such Google apps as YouTube, Maps, Chrome (in full-screen only) and Duo, the recently released Android 8.1 beta reveals that streaming video app Netflix will be supporting Picture-in-Picture once Android 8.1 is installed on an Android flavored phone.
source: AndroidPolice
Things that are NOT allowed: