(this is placeholder until subscription functionality is ready, but useful in the meantime…)

Use aggressive settings and uncheck the following:

1. File API Checking this prevents the video from playing.
2. Fullscreen API Checking this prevents exiting fullscreen using the keyboard shortcut or the icon at the bottom right. It can only be exited by pressing Esc.
3. Media Source Extensions (thanks @jawz101) Checking this buffers the video but does not play it. It doesn't load comments too.
4. DOM Parsing and Serialization Checking this disables subtitles.
5. High Resolution Time (Level 2) Checking this makes the video player always show the "play" button whether the video is playing or on pause.
6. DOM Level 4 Checking this causes general breakage. It breaks the sidebar. Logo is gone. Buttons at the top-right are gone. Main page does not scroll down. Only top three rows are displayed. Related videos are gone. Like/Dislike (and adjacent) buttons are gone. Only two comments are loaded.
7. Timing Control for Script-Based Animations Checking this causes general breakage. Sidebar does not load immediately. Buttons at the top-right are gone. Main page does not scoll down. Only top three rows are displayed. It makes the video player always show the "pause" button whether the video is playing or on pause. Related videos does not load immediately. It only shows one item with no thumbnail. Like/Dislike buttons and description do not load immediately. Comments are not loaded.
8. HTML: Channel Messaging Checking this makes searching on the main page non-functional when pressing enter. Clicking the search button will still work.
9. CSS Object Model (CSSOM) Checking this makes the two buttons at the top-right (Youtube apps and Settings) not function. Seeking the video timeline using the mouse is inaccurate.
10. execCommand Checking this disables copy commands from the video player's context menu.

Or you can import this rule:

[{"p":"*.youtube.com","s":[2,3,4,6,7,18,25,26,29,31,32,33,35,36,38,38,39,44,46,48,50,51,52,55,55,58,60,62,63,67,68,69,72,73,74,75,76,77,78,79,80]}]

Use aggressive mode, but enable Selection API (thanks @jawz101!)

Use aggressive mode, but enable HTML: Channel Messaging, HTML: Web Storage, Selection API