RU-vid videos (and really any media) uses 4:2:0 chroma subsampling so colors are shared in groups of pixels. 4:4:4 is pretty much mandatory for pixel art/fonts (things with sharp edges). I upscale 1080p to 4K by duping pixels 4 times, this makes 4:2:0 the same as 4:4:4 and keeps full color info