Vulcan physiology MUST be somewhat similar, since we know of at least one Terran-Vulcan half-breed, which means that Vulcans and Humans are alike enough that they can inter-breed. Of course, not quite sure how that squares with copper-based blood… 
We know from “Journey to Babel” that Spock’s blood has human elements that must be filtered out before it can be used in a transfusion to another Vulcan.
I wonder what the Vulcans eat that is their “spinach”? 
Good question. Because of their nonviolent beliefs, even their vegetarian diet is limited to the simplest forms of vegetables.
Emotions are just the jive speak for hormones and instinct.
Hormones and instinct exist as a result of evolutionary processes to cause an organism to perform in a way that is beneficial to the species, rather than for its own, logical best results. Simple curiosity is, effectively, an emotion.
It’s unlikely that a species like the Vulcans (as described - not necessarily as displayed) would come out of an evolutionary process.
Though, it is conceivable that a species, like humanity, might decide to genetically engineer themselves to be more stable and reasonable, as the ability for any random idiot on the street to use generally available high technology to create nuclear bombs, plagues, etc. It’s probably the most reasonable alternative when the other option is eventual, inevitable self-destruction.
Trying to fanwank all the contradictions in Star Trek is a futile exercise, because Star Trek isn’t science fiction - it’s science fantasy, like Star Wars. It is full of impossible science, logical contradictions, and technobabble. It’s the product of 50 years of different writers, producers and directors all trying to put their stamp on the universe.
It appears that Vulcans voluntarily decided to give up emotion, and that this choice eventually expressed itself genetically, as an example of Lamarkian evolution. But who knows? The ST universe is so screwed up that you can offer any explanation. Maybe they used Vulcan CRISPR, or maybe they did it through eugenics, by killing or sterilizing children that showed too much emotion.
Or maybe the Space Amoebas of Rigel VII inverted the polarity of their trans-phase warp inverter, which created a subspace rift and sent them back in time to early Vulcan and they removed emotions from Vulcans with a dilithium-powered brain phase-wave injector,
Or in short form: it’s magic. Might as well ask how Tolkien’s Orcs evolved to hatch from some kind of slime pod, fully capable of talking and fighting.