There is no silver bullet when it comes to using Unreal over traditional Maya based previz/production pipelines. Unreal is still a mainly a sandbox production environment that services games rather than a shot based production environment that services downstream departments. That's changing slowly as unreal and traditional vfx technologies converge around USD and less around the existing unreal or Maya toolsets.

The way we see Unreal adoption in a VFX studio long term is either as sandbox previz/postviz where artists do as they please or as a realtime renderer where the work is done in other software (maya, houdini) and previewed and rendered in Unreal much like you'd send it to arnold or vray