Is 8 Bit 4:2:0 chroma subsampling "good enough" for chroma key?
&quot;Good enough&quot;? Sure. I wouldn't love to work with subsampled footage for keying, though. You want to maximise resolution, minimise or avoid subsampling and avoid spill. If your screen is well lit, you got the best circumstances.
So yeah, on paper, a chromatically subsampled file will give you more artefacts and jagged edges in your matte compared to a prores4444 or raw-recording. It is still a workable compression, though. Just try to optimise everything else I mentioned.