Chiss biology
I've been thinking.
About genetic similarity between Chiss and humans. Other than eyes and skin color, Chiss look exactly like humans, but visual similarly is not a good indicator of genetic similarity (a pug and a great dane are same species, while rabbits and hares are not)
Different species ⬆️
Same species ⬆️
In canon Chiss are a different species than humans, but have a common ancestor not long ago.
Usually, the definition of a "different species" is that they can't produce a fertile offspring (or any offspring).
Visual
I checked and it seems there are no animals that can see thermal radiation. Some fish see a bit more into the infrared spectrum than humans do, but not enough to match Chiss vision. We have Thrawn able to tell quite subtle differences in heat inside a building when looking from outside in Thrawn: Alliances.
Interestingly, it seems being a warm-blooded animal would interfere with the infrared vision since the internal heat of its own body would overwhelm anything that one would see further away from the body.
I don't know how scientifically accurate we want to go in a universe where there is sound in space and gravity strong enough to walk in an asteroid inside a space slug, but if Thrawn is able to see increase in heat when humans have strong emotions, he would have to be a cold-blooded animal, like frogs and fish and snakes etc.
Speaking of snakes, they can sense heat with special receptors in pits on their head, but they can't see it, and they have to be quite close.
However, Chiss are not cold-blooded. In Thrawn: Treason Thrawn sees Un'hee and Vah'nya's body temperature increase.
Their hands are clasped together, the fingers white-edged from the strength of their mutual grip. Their facial temperature is elevated.
That's it. This post has absolutely no point.