I've only done some causal gaming on high settings - gpu temps never broke 60 Celsius. Only stress testing w/ 3dmark was I maxing out in the high 70's. To me that's a very comfortable range to be in. Proper mounting of the psu, plus a good pull/push set up of your case fans will keep this cards temps under control. I'd certainly recommend this case + card setup.
As far as noise is concerned, yes I barely hear the computer when it's on. I don't go around listening to dozens of different computers, but this build is the quietest PC I've ever owned. When the pc is in an idle/sleep state it makes no sound at all.
Search for pc desk mount. There's all sorts of options. I happened to buy one straight from the desk maker.
Fully brand, Jarvis Bamboo
It's fairly easy to take on and off. It's attached via a clamping lever that hugs the case. You just pull the lever to release the case.
Yup. The desk is a motorized standing desk, so i have the pc mounted to the frame underneath the desktop.