Wow I didn't even know it was possible to clean a gpu ! I'll try that, I've only dusted the things a few times since I got it.Ok, so now I know what your GPU and PC case and fans are for the most part. GPU itself looks to be decent and should have sufficient cooling and your PC case isn't some cheap garbo product.
With that, then my next question is, have you cleaned the inside of the GPU by taking it apart, dusting off the fans and changing the thermal paste , maybe also thermal pads (this is more of a lest resort) ?
The problem with the Ampere architecture (RTX 30 series) is that despite limiting the fps, if you game asks for your GPU to give it all, it will do it. My RTX 3080 is undervolted pretty heavily and yet it can still exceed that when a game demands for it. That is the experience of these cards. It's all about how much Wattage the GPU pulls at the end of the day and how much the cooling can efficiently cool.
HS2 is quite heavy on my GPU, not going to lie, but I managed to tame it partially by limiting fps and tuning some settings and only cranking them up when working in studio.
Lowering resolution can also help, though I do wish there was a upscaler mod to help battle the demanding nature of GraphicsMod and bunch of Hanmen custom shaders + the not so great optimization of the game.
Also, which settings did you bring down in HS2 ? I was a bit afraid of breaking something so I only removed shadows (I left ambient occlusion), and some of the lights in the F5 pannel. It doesn't feel enough though.
I've also lowered the aliasing but it starts becoming ugly after that