Depends on hardness too.
IF the originals are 2mm, but you get 2mm that are really hard, you're liable to break something. In the case of such hard pads, you would need shorter than what the manufacturer used.
IF the originals are 2mm, but you get pads that are a bit shorter than them, you can end up having to stack pads to get proper contact with the heatsink.
Keep looking/asking around. Pad replacement is a very niche thing. Try gpumining reddit or hardforum's mining & cryptocurrency section. You'll likely have more success with those. [TechPowerUp has one too.]
You shouldn't be having Vram temperature issues though..? It's GDDR6X found on 3070Ti and up that has high operating temperatures.