Even if your card is putting out 120fps or 1500fps, you're not benefiting from those extra frames. 60Hz is your monitors refresh rate / maximum amount of frames refreshed per second. It is a waste of resources for your card working overtime to pump out those extra frames that the monitor can't display. With v-sync off, your card is putting out as many frames per second as possible. With a 60Hz monitor, the most you will see is 60 FPS, therefore, there is no point in having your card struggle to put out hundreds+ frames per second.
If the GPU and other components are overstressed, temperatures will rise. This can lead to overheating. Stability and performance will be affected as a result. I can defiantly believe others have burnt out cards before. If a computer has high temperatures mixed with not so great cooling & ventilation then that's a big problem.
Reshade will drop frames... When I use Reshade, I get frame drops even with a GTX 1070 and before that, a GTX 980. Your card is just enough to handle it but expect Reshade to affect game performance. Admittedly, the latest version is much more stable frame rate wise vs the first couple of versions.
The game alone without mods or overlay tools like Reshade can have frame drops when zooming out, camera movement, or even max fast forward. I use v-sync and I get a stable 58-60 frames unless I'm playing a very large save then I can see drops down to 50 frames when zooming out, camera movement, and max fast forward.
