I think that the MRA smartphone app is probably the best planner to use for the XT when on the move.
It knows the difference between the different types of points, it gives you the track that you can display alongside the route and which you know will never change and it transfers to the Zumo direct through the Drive App.
As long as you are aware of the differences between its gpx versions and what that means for the route, it gives you everything that you want.
In case you don't know:
Gpx v1.2 sends the actual route that you planned (if you use the HERE maps). This will stay put as long as the XT is not allowed to recaclculate. If it does recalc, then the entire route will probably change because v1.2 does not transfer the shaping points.
Gpxv1.1 transfers the Trip as a sequence of Via and Shaping points, but does not transfer the route. This is left to the XT to calculate.
Both methods also transfer the track.
Detailed explanation with pretty pictures, here: app.php/ZXT-P76
Having Garmin zumo XT problems? there is loads of help and advice in this forum