I was thinking of using fibermesh, but Unreal 4 can’t support that, so is there a way to turn fiber mesh into planes or should I just sculpt the hair by hand?
You can greatly reduce the fibres density and up the scale to give very plane like geometry. Or us one of the Insert brushes to draw out plane type hair. Loads of ways to get it done.
Would the planes move in Unreal 4 via the game engine or is that something that’s animated when doing other character animations?
You would have to rig them the same way you are (presumably) doing it with plane hair.