Optix is not compatible with UE4, they could integrate it in some way but there’s currently no connection.
In terms of rendering capabilities, you can use Matinee or Sequencer to render to a video or image sequence at whatever resolution or framerate you want. It also supports .exr output.
For the render quality, it’s not something you can compare to a typical 3D rendering software, it’s designed for realtime graphics and to get the best results you have to configure things differently. For doing things like Archviz it can be a huge speed boost when doing an animation. Rather than waiting an hour for a frame or having to pay for a render farm you can get frames rendered in less than a second once things are set up properly.
It would be really innovative for unreal engine as OptiX supports interactive path tracing where UE does not have that feature. It just stick with the prebaked path tracing algorithm.
But as the rendering is involving rapidly from photo-realistic to hyper-realistic, and the GPUs are also improving, I believe future path tracing will be a good option along with ray tracing.
For offline rendering, its already used. For realtime, brute force RT will never ever be used, atleast within our lifetimes. Tech will reach the physical limit before we ever turn minutes per frame to frames per second.