There two types of tracks
Routes and courses
Routes have lots of points and you can't use map mode because fenix will try two find a solution for each point and that take a lot of time. You have to use…
My Fenix 6X calculates a simple route for 15 minutes. If it has any problem on the route, I have to restart the navigation and it calculates again for 15 minutes. Also, as caspervet describes, if the navigation has any problem, or if you go a bit off route once, it changes to trying to bring you to the destination over a direct line. These 2 problems make the 'follow map' type navigation pretty much useless. I have experienced it multiple times that this watch is not going to bring me back home : - (
There two types of tracks
Routes and courses
Routes have lots of points and you can't use map mode because fenix will try two find a solution for each point and that take a lot of time. You have to use follow mode. The is not a fenix tbt navigation but a breadcrumb solution. However,, some programs like connect put additional information on the route that can provide TBT information.
Courses have a small number of points. The points are more land marks that fenix must pass. If you use follow mode you will get straight lines between those points. If you want navigation you must use map mode..the actual calculated route could be different from what you espected because it calculates using an algorithm like minimizing distance.
Strava komoot etc exports routes not courses. So you must use follow mode.
To use map mode you can use explorer app to draw the course or convert the route in to a course with a program like basecamp