I stream all of my own content with an Apple TV and Plex just fine. I don't know what problems you've had there. It even handles exotic stuff like Hi10P h.264.
How's your surround sound? tvOS 26 decided at the last minute not to support audio pass thru, which means only the pretty basic audio codecs that the AppleTV itself can decode are supported. That's an extremely limited number, and I believe only the very basic 5.1 is supported for any surround options.
