If you only have a start and end point, you have the track.
If you compose the route properly, a GPX 1.2 also works perfectly, I don't use anything else.
If you use the connector, a GPX 1.2 will also work well in an XT2
If you use the Tread app, it is best to use the GPX 1.1 and its track, because the Tread app and the Garmin Explore website cannot yet process route files properly. A track is processed properly.