Well, I briefly tried Elite Dangerous with the maximum DSR oversampling (4K, I think) and the fans went crazy. There are three of them on this card, it sounded like a hairdryer.
Nothing else has taxed it quite that much, so far. It just cruises through every other game (my monitor is only 1920x1200, so oversampling seems to be the only way to bring this GPU to its knees).
Come on, Apple, they've released the mobile versions now. There's no excuse not to get these in the next generation of real Macs.
I'm not much a PC gamer, but the hardest one I had running was Witcher 3 (I think it tops out the GPU), and the EVGA card I have is OC'd out of the box and it runs around 75c under load. The fans kick in and spin at around 50%, but I set a curve on the fan to hit it higher a bit. It's very quiet.
If your case has decent cooling, the GPU shouldn't be hitting the fans at 100%. I think it's the cooler that matters, and from what I've seen the EVGA ACX coolers are really good and quiet.
Also really well programmed apps/games won't hit the card that hard, this thing is a beast and can run on low power for most 3d games. I run at 1440p.
Also regarding the mobile versions, it's crazy they actually put the FULL 1080 Pascal GPU in laptops now (albeit they're fat and wonky)...but it just shows how far GPUs have come.
I really doubt Apple will use nVidia again for a while, they prefer AMD and I assume they get really good prices en masse from AMD on their lower tier GPUs. They even cut a deal on the Trash Pro GPU's where each GPU cost $600 instead of $3000.
I just really wish Apple would give the option to go between AMD and nVidia on iMacs and Mac Pros. They use Xeon and workstation components so I assume they don't want to move to a full consumer desktop platform with the Mac Pros, which is sad because Xeons are the same as i7s, except they usually have more cores that run at lower clock speeds per core.