I think different races are tied to different realms of the Shadowlands whether by normativity (eg all Trolls go to The Other Side ruled by Bwon and his boss presumably Muehzala, though maybe it’s because they all render devotion to him), by some sort of contract magic (eg Night Elves are tied to the Emerald Dream and we are probably gonna get a Wisp - Ardenweald connection), or by the choice of the Arbiter (eg souls going to Rivendreth, Bastion, or Maldraxxus).
The latter of which only occurs if there’s none of the former or if the soul doesn’t want to go to either of the former. Though at the moment we don’t know what happens if a soul promised to Bwonsamdi doesn’t want to go to The Other Side but instead wants to go wherever the Arbiter wants them to go.