Which way to face a character?

I imported a character I’m working on and when it imports it faces down the +x axis. I notice also in the marketplace submission guidelines it also says that models should face in the +x axis. So I assume I’m doing it right.

However, when I open my model in the editor or the retarget manager in UE4 it is facing to the right (as that is the direction of the +x axis), instead of facing the camera. I’ve download the free models from the marketplace and I notice that they all face in the +y axis so that they face the camera. Even the blue man that comes with UE4 faces down the +y axis. It seems like the camera’s in the UE4 editors are set up to view models facing down the +y axis by default, so I always have to rotate the camera to view the front of my model.

I’m very confused by this now. Why does the engine treat +x axis as forward, and the guidelines say to use +x axis as forward when all the editor view ports treat +y axis as forward and the models in the marketplace and in the engine content treat +y axis as forward? What is correct?