Most devices that support AirPlay receiving, can also have the Apple TV app on it to stream directly without a separate AirPlay sending device. Verify if your device is on the list.
Apps that offer in-app AirPlay controls, those can switch apps or have the screen sleep while continuing streaming. Other apps that rely on screen mirroring video capture, those will need to have to retain focus on the program on the sending device. So it depends on what you want to stream.
AirPlay content follows the captions and subtitles settings of the receiving device. For the Apple TV box, that is the general device settings for closed captions or subtitles. For third party devices that offer AirPlay support, that settings is part of AirPlay Settings.
Apple TV app - Devices - Apple
↳ Apple TV app-supported devices
↳ AirPlay-2 enabled TVs and devices
Use AirPlay to stream video or mirror the screen of your iPhone, iPad, or iPod touch - Apple Support
If screen mirroring or streaming isn't working on your AirPlay-compatible device - Apple Support
Get the Apple TV app or Apple TV+ app on your smart TV, streaming device, or game console - Apple Support
All the ways to watch Apple TV+ - Apple Support