The MSI Radeon RX 6800 XT Gaming X Trio has the best cooler out of all RX 6800 XT cards we've reviewed so far. With just 67°C, this triple-slot, triple-fan design runs extremely cool, yet stays very quiet at the same time. As expected, idle fan stop is included, too.
It draws power on both occasions(idle and load) but the degree of power drawn vastly varies between the two. If the GPU is pulling the same amount of power in idle as does when in load, then the drivers are either not installed or they're corrupt.
The GPU will only pull power from the PSU as is needed but it has a ceiling as to how much it can draw. Also, the power you see used is by the entire system, not just the GPU.
No personal experience with mining. Assuming youre mining Ether I found a quick reference on Reddit saying that sometimes GPU usage doesnt appear in task manager with some mining software even though its working. Did you check in any 3rd party monitoring software like GPUZ or HWINFO?