Hi,
The only difference between OpenGL and DirectX is that the green channel is flipped.
If you’re building a Marketplace asset, I’d recommend using DirectX as it’s the default in Unreal. User’s won’t have to think about it. If they’re exporting to a ddc that is defaulting to OpenGL, they’ll have to flip it in the ddc.
Quixel Megascans, for instance, are using DirectX.
Hope that helps.