What should i set as front axis while exporting fbx from blender to unreal?

want to know the fbx export settings form blender to unreal. in some forums it is mentioned that +x is forward, but when i tested in my pc, +y is forward, because when i align the scene in front view, +y is pointing towards my side. but it is suggested for fbx export we have to set -x as forward, why is that?

what should i set as front axis while exporting fbx?