you also have to note that Vulcans and Romulans are the same species.
Negative. They are relative by a common ancestor. I do not believe Vulcan physiology is identical to that of Romulans.
I do agree with the general thought in your post. All of this talk of Spock "getting in touch with his human side" is erroneous. He could as easily be in touch with his Vulcan side when expressing an emotion, considering that Vulcans are inherently an emotional race, even moreso than humans.