I have garmin 6x, which comes with preinstalled maps of my country (CZ). If I open garmin connect and try to plan route there, only some substandard map is available, where all trail marks are missing. I can use online services like mapy.cz and export gpx, but that approach for said service does not allow me create off-road parts or futher modify created gpx. Then we're back to paid preinstalled maps in watch — these are fine, BUT works only in watch themselves or hypothetically in Garmin BaseCamp, which should work, however I never saw it working since loading maps takes hours, and every click takes minutes.
So I'd like to ask for your experiences. How do you prepare your routes?