Blender and UE4 uses z as up. Which was intuitive to me having been taught that in school but Looks like industry standard for 2d focused engines use Y up based on this comment from 2009. What a mess.

Maya and Unity both use the lefthand axis system which has Y as world up. Max is the one of the few that uses Z as up (DOH!!)

2022 comment:

Maya is fully able to translate between its own (Y up) and UE4’s (Z up) on export, so you can work “upright” in both without any alterations.