[Tadanobu]

Yeah, I made some new tests and I can confirm that. Higher numbers give higher bitrates while the encoding speed is not significantly faster. I can't see any good reason to use it at the moment.

So, here are some screenshots for subjective comparison. Source is 8bits 1080p, encoded with an i7-8750H using ffmpeg.

Speed went from 0.01FPS (-q 20 -enc-mode 0) to 8.07FPS (-q 50 -enc-mode 8). I personally find -q 20 -enc-mode 4 to be a good balance but it is still as slow as 0.89FPS.

Cropped and zoomed in
https://i.imgur.com/Q0IDhhL.jpg
https://i.imgur.com/JuviCld.jpg
https://i.imgur.com/jBSR00P.jpg
https://i.imgur.com/XCZucKs.jpg
https://i.imgur.com/Sw9fTs5.jpg
https://i.imgur.com/fzT3jba.jpg
https://i.imgur.com/RMlXto3.jpg
https://i.imgur.com/FM7Iwj8.jpg
https://i.imgur.com/ZoNvbsh.jpg
https://i.imgur.com/YQiPuvE.jpg

Full frames
https://i.imgur.com/y6VX0j9.png
https://i.imgur.com/9QHBAnK.png
https://i.imgur.com/IuhcV8j.png
https://i.imgur.com/IkDEXT5.png
https://i.imgur.com/oHFdv3Q.png
https://i.imgur.com/mCavZbf.png
https://i.imgur.com/G4n1vtt.png
https://i.imgur.com/TJ72o5A.png
https://i.imgur.com/3wWDFld.png
https://i.imgur.com/B83rdXk.png