I've always regarded Vorik and Taurik as the same person.
But when it comes to Tuvok, I have some own theories:
The Tuvok lookalike in "Starship Mine" is actually Tuvok's evil brother Devor, the black sheep of the family who have left his home, denied his relatives and became a criminal. For some reason, Tuvok has never mentioned anything about Devor (or Devok if you want it more Vulcan), maybe for the same reason as Spock never mentioned his brother Sybok to Kirk or McCoy.
As for the Tuvok lookalike in "Generations", let us just assume that it's Tuvok himself, on a brief stint with the Enterprise. Why not?
The Tuvok in the DS9 episode "Through The Looking Glass" was a mirror Tuvok.