I recently came across the "Heritages and Halfbreeds: Shadowborn" after watching a youtube video by MrRehexx titled "What They Don't Tell You About The Shadowfell". In his video he explains that there is a shadow variant to each person on the prime material plain. Would it be viable to have Shadowborn orcs, dwarves, tieflings, etc, etc? If so, would you just use the Shadowborn traits/subclass, and have them appear as an orc, dwarf, etc? Or would you give them their base racial traits, and choose a Shadowborn subclass (Thirllseeker/Gloomling)? Feedback, and balance suggestions would be greatly appreciated. Thanks.

That's homebrew, so you can do whatever you want.  We don't have official content on playing anything from the Shadowfell but Shadar-Kai, not even Shadar-Kai halfbreeds, if they even exist - we have no rules on half-Eladrin, either.  They might have too much fey in them to breed with humanoids.

I understand that it is homebrew, and there is no official content as of yet. I was trying to ask the community how they would go about doing this.

shadow born are epic i was playing one in a campaign recently and at level 6 managed to get all the way up to +14 in stealth i roll stealth and vanish

In my opinion you should make each shadow unique compared to it counter part.

omg i can relate i love using shadowborns as races even i they are homebrew