Do we know which side is heaven/hell? Do we know which elevator is heaven and which is hell? In the Death Billiards movie, it seems kind of debatable. As well as the first episode of Death Parade, did the wife or husband go to hell? Does winning the game have any bearing on this?

Also, not sure if this is any kind of hint, but the beginning of the episode, when the couple enters the room:



But at the end of the episode, the couple leaves in the same elevators but the masks have been switched:
We know that the final result is that the husband gets sent to heaven and the wife to hell:


  Takashi gets reincarnated and Machiko gets sent to the void. Wikipedia


The bartender also states that the husband goes to "heaven" and the wife to "hell". This is in the scene after the end credits for the first episode. I believe you may have missed it or Funimation could have neglected to include it.

As you mentioned, the Funimation subs say Heaven and Hell instead of Reincarnated and Void. I believe that this is due to localization, since most English speakers are going to be more familiar with the concept of "heaven and hell" after death, rather than "reincarnation and void". 

The mask indicates where the people in the elevator go.

My reasoning is that the husband arrives in the hell elevator because he killed the couple to begin with. Then when it's revealed that the wife cheated, she gets sent to hell.