One other trick as well, if you want to quickly set x forward before exporting the scene using this method if you select all the meshes you want to affect and then enable transform only origins in local space you can just do r z -90 and have x forward.
If you have instanced meshes then make sure you select all of them when you do it and blender will lock them in place adjusting the rotation to compensate which is a neat trick. you can test it out if you leave one out of the selection it will spin like they would if you just went into edit mode and moved the mesh but with affect only origins selected and doing it like that all the ones you have selected stay stationary as the pivot moves.
then in unreal you now have x forward as well if you want that for consistency.
