Apple TV streaming apps running slow

Okay. Then it seems that the issue might be with these apps or the remote servers that they connect with.

Try this for any misbehaving app:

1. Force-quit the app, then relaunch and try again.
2. If the issue persists, force-quit the app, restart the device, then relaunch and try again.
3. If the issue still persists, delete the app, re-download and try again.
4. If the issue still persists, then contact the app developer for further assistance.

speed test shows over 800 mps consistently

Did you measure that on the Apple TV box itself? If measured elsewhere, then some factors of possible slowdowns may not be included.

Speedtest app - App Store preview - Apple