The YouTube site has gone through many redesigns over the last few years. Each time, features are added and taken away, which may not suit your preferences. If you want to view videos with fewer distractions, or stop the new autoplay feature, Magic Actions for YouTube has you covered.
Auto HD mode
This is extremely useful if you're constantly changing the resolution setting from 480 to 720, or even 1080. Each video you load will use your resolution preference. To adjust this setting, head to a YouTube page and click the Magic Actions icon in the omnibox, then click on Options. You'll see the supported resolutions under "Enable AutoHD."
Cinema mode (seen at top)
This is one of the more useful features, since it will definitely make YouTube a bit easier on the eyes. Usually there are recommended videos piling up around the one you're watching, and a comment section overflowing with trolls. Instead, Cinema mode will place your video in the middle of the screen, surrounded by accent lighting. To enable this, just click next to the video in the blank page space. If you want to change colors, click the icon all the way to the right and a color bar will appear. Don't forget to save your changes.
Google has been testing a "feature" that plays the next video in line after the one you're currently watching. If you don't want this to happen, you'll have to use a plug-in like Magic Tools for YouTube, because they don't have a reliable toggle for it (yet). Click the Magic Actions icon > Options > check the box next to Stop Autoplay.
This plug-in also features the ability to take screencaps of what's playing, apply filters and mute annotations. Check it out and leave your thoughts in the comments.