Change display resolution on a ipad pro

I’m unsure of your expectations - but consider the following...

iPad has Screen Mirroring - that reproduces what you can see on the iPad display - on an external TV or monitor. Screen Mirroring does exactly as its name implies; the iPad screen is reproduced on the external display, preserving the aspect ratio of the iPad screen.

AirPlay extends capabilities of iPad - permitting display of playing media content (either download or streamed) to an external TV or monitor, at full resolution and aspect ratio of the source material, independently of the iPad screen.

Screen Mirroring of any content will preserve the screen aspect ratio of the iPad. Your TV may allow you to “stretch” the content mirrored display (removing the black side-bars), but will introduce distortion.

When using AirPlay, video media content will display content in its native video aspect ratio; as such, 1080 Widescreen content will be displayed in its widescreen format on your TV. Non-media content will not use AirPlay - but must instead use screen mirroring if viewed with an external TV/monitor.