Update: Added results for Vivaldi and Brave.
What a journey this has been… and saw the mess the README file has become. Well, I polished the file. It has a new section “Determine the VAAPI driver to use”. The flow is nicer now.
There are three new sections for Google Chrome, Vivaldi, and Brave. For the first time, I saw the Video Engine (NVIDIA) being used (VP9 media) along with the GPU while watching videos. This is unlike Chromium and Firefox where the Video Engine is not utilized, just GPU.
In closing, I ran various benchmarks on the web. Note that results can only be compared to other browsers running on the same machine. Difference CPU or GPU may very likely produce different results.
Version
Chrome 97.0.4692.71 Firefox 96.0 Brave 1.34.80
Chromium 99.0.4829.0 Vivaldi 5.0.2497.38
Chrome 528.0 (*) Firefox 512.0 Brave 521.0
Chromium 526.0 Vivaldi 526.0
Chrome 212.0 (*) Firefox 172.0 Brave 158.9
Chromium 147.2 Vivaldi 153.0
Chrome 58623 (*) Firefox 29641 Brave 57586
Chromium 57215 Vivaldi 56398
Chrome 184.5 (*) Firefox 118.8 Brave 175.4
Chromium 178.2 Vivaldi 172.2
Chrome 1002.0 (*) Firefox 690.7 Brave 767.2
Chromium 627.3 Vivaldi 783.2
Chrome 137.8 Firefox 116.5 (*) Brave 154.7
Chromium 147.5 Vivaldi 150.2
Chrome 3.0 (*) Firefox 3.1 Brave 3.3
Chromium 3.4 Vivaldi 3.4
Chrome 43.4 Firefox 116.0 (*) Brave 33.1
Chromium 31.8 Vivaldi 34.1
Chrome 2852 Firefox 2672 (*) Brave 2916
Chromium 2803 Vivaldi 2894
Chrome 306 Firefox 310 (*) Brave 272
Chromium 280 Vivaldi 285
At last, I hope the project is finished. Can that be for real? 
What to make of this? Depending on the site or web application, Firefox may feel faster to you. See the StyleBench results above. Google Chrome and variants are quite fast otherwise. Brave and Vivaldi spend less time loading pages due to blocking creepy ads. IMO, enjoy the browser that you like using.