How to Fill tv screen from iPad

Mirroring your iPad display to an external TV or monitor will preserve the iPad aspect ratio. Viewing video from a video player App, such as YouTube, should display the video content in its native aspect ratio and resolution.

Put another way - when Mirroring your iPad display to an external monitor, expect to see black bars to infill where the iPad screen doesn’t match the monitor screen - whereas 16:9 video content will fill the screen of most 16:9 monitors.

One caveat, some monitors have settings that attempt to “stretch” the display content to match the aspect ratio of the display. This feature, if present, can introduce distortion (e.g., “people” develop strange proportions - such as short and wide).

I hope this explanation and clarification is helpful to you.