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

Expand the drop-down list and select the monitor you want to play your game on (e.g., Show only on 1 or Show only on 2). It moves all content to the selected screen instantly.

Select "Second Screen" from the list of options. Click "Extend" to extend the space of your desktop across your two monitors. The settings automatically save.

Extend Display will increase your workspace so that it extends onto the display. Selecting Mirror For with the name of the other screen will make macOS show the same image on both displays.

If you want to set up dual monitors for sharing presentations with Zoom video, your job isn't done just yet. Here are some further tweaks you need to do.

Mac 911 Full-screen applications and multiple monitors Mac 911 By Christopher Breen, Macworld JUN 18, 2012 3:30 am PDT ...