Are you going to produce 4k for Youtube/online streaming? If so, compression is still going to affect the video way more than “only” down sampling from 8k-16k. Even 1080p video up-scaled to 4k looks better and passable compared to Youtube’s 1080p bitrate/compression. Also the higher the resolution, the less you’ll see aliasing and artifacts, so you probably wont need something like 32k to make it look as clean as 1080p down sampled from 16k.