A small PSA about a bug I've encountered for quite some time, and the solution I found searching (answer was a small old thread on EU WoW forums).
The bug: When AA is on, your gpu temps will max out (93 C for me) any zone, any time, any load (40-60% gpu usage, will still go up to 90s C and sit).
This might be NVidia only? My graphics card is a MSI 1080 Armor OC +175 core, +500 memory, fans at 100% above 60C, in a case with 6 140mm fans (Phanteks Enthoo Luxe with drive bays removed), nothing blocking the front fans to the gpu, and it has plenty clearance under its fans. Running on a 1080p 144 Hz freesync monitor.
Turn AA off, temps go down fast. It is usually in the high 60s if the load is lower, and low 80s if it is a big open area with lots of things to render near and far on a warm day. All other settings remain the same.
To be clear on this as well, I also play Destiny 2 now and then. Even when that game is at max settings with 150% scaling for fun to stress it, the card will be at 100% usage, but the temps stay in the 70s most of the time.
So if you are seeing unusually high temperatures for seemingly no reason; try disabling AA. I've reported the bug a while back. Searching the forum found an almost 3 year old post, mainly discussing AMD RX500 series card the OP had.