The Vulcans are closely related to the Romulans but, unlike the Romulans, Vulcans are trustworthy albeit calculating. Both have been around the Star Trek universe since the original series.
The Vulcans’ makeup design has changed little over the years – essentially pointy ears and slanted eyebrows – but then came an alarming tendency for Vulcans to adopt unflattering Romulan hairstyles: indeed it had got to the point where it appeared that most of the actresses playing Vulcans or Romulans were sharing a single wig.
Too late, too late they suddenly started to show a little individuality again at the end of the final season of Enterprise.
Michael Westmore was the makeup designer and supervisor for all the Star Trek television series other than the original series.
Admiral Sitak: In the Deep Space Nine episode ‘Favor The Bold’ Admiral Sitak (Ericka Klein) together with Admirals Ross and Coburn approved Sisko’s suicidal plan to regain control of Deep Space Nine.
Dr T’Pan: In The Next Generation episode ‘Suspicions’ Dr T’Pan (Joan Stuart Morris), a Vulcan scientist and director of the Vulcan Science Academy, was suspected – along with the Klingon Dr Kurak – of being a saboteur and murderer; they were only cleared when the real murderer confessed.
T'Paal: In The Next Generation episode ‘Gambit’ T’Paal (Robin Curtis) was an agent of the Vulcan isolationist movement pretending to be Tallera, a Romulan mercenary. As Tallera, she infiltrated Arctus Baran’s mercenary crew to acquire fragments of the ancient weapon known as the Stone of Gol but was captured and turned over to Vulcan Security. I don’t recall any mention of how T’Paal acquired her Romulan forehead ridges: presumably her appearance was supposed to have been surgically altered for her undercover mission. Robin Curtis was of course no stranger to being a Vulcan; she had played Lieutenant Saavik in both The Search for Spock; and The Voyage Home.