what are the advantages of UE4 for just rendering animations/cinematic scenes

I’ve seen some amazing render work done in UE4 lately from this artist:

it made me wondering what the benefits are of rendering something in UE4 (a game engine) versus your typical 3d rendering software if all you need is still images or small animations.

Are there any inherent advantages besides the supposed 60 fps?

And the other major question I have is, most people cant believe that those renders were done at 60 fps considering polycount and detail. So the question is how many polygons can UE4 take while maintaining a minimum 30fps rendering in real time with say, a typical Nvidia 1080/1080 ti?