It’s a bit unconventional to write for an untuned or unpitched instrument on a standard pitched staff with a pitched clef, whether it’s a G clef or a C clef. In Dorico, percussion maps can’t take effect on a pitched staff: whatever pitch you specify on the staff is the pitch that will be played out to your chosen endpoint. You can transpose it by one or more octaves easily enough (using an expression map) but really this is not how things are intended to work.
I’ve already provided you a link to a detailed walkthrough of setting up a percussion map, but I’ll post it here again:
By default, the cymbal instrument does indeed look for the Natural playback technique, so you need only define a mapping in your percussion map for the standard clash sound for the cymbal, and make sure it uses the same instrument and playback technique as the cymbal instrument in your score.