A very good extension and does a lot for customization. I love the extension's wide range of DeepDark themes and their built-in ad-blocker. They have a mini-player for scrolling down to the comments and a pop-up player for switching browser windows (only available on desktop). It can disable autoplay and set your volume at a fixed position. It also has a volume booster for when the video is too quiet. I can also switch the quality to my preferences.

Works great, I especially love being able to screenshot videos and get exact speeds. Being able to move the control panel to a specific place on the screen would be nice- currently, it's either below the video or centered. Definitely enhances YouTube!