1) if your device plays 4k, then what are you transcoding from? That's going to be the determining factor, not the 4k output stream. Certainly in a home situati

1) if your device plays 4k, then what are you transcoding from? That's going to be the determining factor, not the 4k output stream. Certainly in a home situation, that's likely to be direct stream. If your source files are 8K or higher, I wouldn't consider you a normal home user. 2) quicksync on a 10g or newer cpu is benchmarked at 4-6 4k simultaneous streams, but a lot depends on the details: container format in particular matters a lot, and so do your transcode options. Color matching for example, is only ever done on CPU. And IIRC AV1 and VP9 are not supported by quicksync (or older discrete GPUs). That said, it's completely correct that you should measure all advice against your actual output device capabilities and source quality.