If you see the same thing on both displays, you should start by making sure the displays are Extended instead of Mirroring ...

Everything you need to know about how to connect a laptop to a monitor to mirror or extend your display.

Duet Display lets you use any Android device as a second screen for your Mac, whether wired or wireless, giving you extra space for multitasking.

How to Use spacedesk to Mirror or Extend Your PC’s Screen Onto an Android Tablet Before you can mirror or extend your Windows PC’s screen to your Android tablet, you need two things.

With Sidecar, you can use your iPad to mirror content to your Mac or extend it to your tablet.