So now after a lot of trying, I put together a tethering outfit for the GFX, which seems to work for my workflow.
The GFX is tethered to the Imac running Lightroom with the Fuji tether plugin pro running mirrored on the Eizo and the Wacom companion. The Eizo is for the stylists, clients can look at the Imac and I am setting everything by touch on the Wacom. works like a charm, tethering is acceptable stable, even pulling the plug doesn't crash the system, previews show up in Lightroom after around 3 second (compared to the Sony A7r2 with around 13-15 Sec). I need to tidy up the cable mess, though....
I am happy for now, tuesday I am going to shoot my first job with this setup