Having worked in the space, I'd have to say hardware encoders and H.264 is pretty dang good - NVENC works with very little latency (if you tell it to, and disable the features that increase it, such as multiple frame prediction, B-frames).

The two things that increase latency are more advanced processing algorithms, giving the encoder more stuff to do, and schemes that require waiting multiple frames. If you go disable those, the encoder can pretty much start working on your frame the nanosecond the GPU stops rendering to it, and have it encoded in <10ms.