>> It's got a ton of optimisations and tweaks to make it run in realtime, but if you're making a movie there's no reason not to spend hours rendering each frame.

That's how it's used though? It only runs real time for preview, but the final product is very much not rendered in real time at all. Obviously it's a very flexible tool that works with what you need and what you can afford - Disney runs it on their compute farm and they can throw the resources at it to render at the fidelity required. But obviously there are plenty of production houses which don't have those kind of resources and they have to make do with less. But then you wouldn't expect Pixar's own pipeline to work in those circumstances, would you.

>> Unreal does have the ability to render out video but it's not going to be the same fidelity.

I really encourage you to look into what's possible with UE nowadays. Custom made pipelines from Pixar or Dreamworks are better still, of course, but UE can absolutely stand next to them.