For our temperature testing, we measure steady-state GPU temperatures under load. A reading under load comes from running A Plague Tale: Requiem for 30 minutes.
As for out of the box thermals, the GameRock does well enough here. It's clearly not on the same level as the Suprim, but the Performance BIOS GPU temperature is on par with the Founders Edition while reducing VRAM temperatures by 6C. The Silent BIOS only runs fractionally warmer too, so I'd say these results are good enough, if not spectacular.