For resolutions over 1080, it's only VP9 (and I guess AV1 for some videos), at least from the user perspective. 1080 and lower have H264, though. And I don't think the resolutions below 1080 are enough to matter for the estimate. They should affect it by less than 2x.
The lots of videos with low view counts are accounted for by the article. It sounds like the only ones not included are private videos, which are probably not that numerous.
The lots of videos with low view counts are accounted for by the article. It sounds like the only ones not included are private videos, which are probably not that numerous.