Quick question: when Microsoft (via Shitware 10) runs video encoding, does it switch off "mitigations"?

What portions of video drivers are missing in various linux distributions that are present in Shitware 10?

How come that gstreamer VAAPi (mpv, VLC) is using 14-16% cpu and on Shitware 10 VLC is using up to 1% CPU and I see 0% on mpv/smplayer? (Same version)?

gstreamer VAAPi,
Intel libva gstreamer/intel media HD
intel gmm

PS. Why intel libva on linux requires CUDA to be present?? What the hell?
and why intel media HD is broken (on compatible hardware)? See e.g. mpv --hwdec=vaapi --vo=gpu --noframdrop=yes Blahblah.mp4 (avc1)