Something similar has been tried and the details of the result can be found here:
https://www.heise.de/newsticker/meldung/Intel-Prozessoren-Kaby-Lake-unter-Windows-7-Geht-halbwegs-doch-3606409.html
Translated with google translate:
"There are other drawbacks: display errors occasional when scaling windows, Google Chrome can not use the VP9 decoder of the Core i3-7100. 4K videos from YouTube run anyway, but with more than 50 percent CPU load the browser leaves single frames. Also H.265- / HEVC-Videos run under Windows 7 only with additional software.
When playing HEVC / H.265 videos, PowerDVD 16 Ultra also uses the hardware decoder and therefore causes less than 10 percent CPU load on the Core i3-7100 at 4K resolution; However, HEVC videos with 10 bits per color channel for HDR do not run.
Because hardware decoders for VP9 and 10-bit HEVC are the main advantages of Kaby Lake compared to Skylake, there is little reason to use Kaby Lake under Windows 7."
Those are the results for 21.20.16.4508, I am interested to know if 21.20.16.4526 corrects those issues if someone tried.
Thanks