Hi @Crest_91 thanks for posting this question.
You can enable PiP in your app using ACS. PiP in Android is done at the Activity level, and you can decide whether you want to enable PiP on the Activity when it goes to background or when your application triggers some specific business logic you want. The later allows you to have a PiP Activity running while you are using other Activities in your application (like a floating window inside your own application).
Since this is enabled on the Activity level, the Activity where the ACS call is in progress can enter PiP mode and you can customize how the PiP experience behaves depending on your use case. For example, you can change the UI on your Activity to show your video preview, a remote video from a participant, or show screenshare stream from a participant, or have mute and unmute buttons, etc. The Android developers link you posted on the questions explains how to setup your Activity to enter PiP mode and how your UI can react to entering / exiting this state, so that you can provide an experience according to the rest of your app.
Hope this helps you in adding PiP to your application using ACS.
Jose.