How extensions are presented (where the icons are and how users access them) is up to the browser. Firefox surely has a unique unobtrusive way.

Regarding documentation: Did you look at the screenshots? Considering that you seem to have missed them, I doubt a text explanation would have helped here. I'm sure you will figure it out. =)

Edit:
1) Understood. I might add a brief explanation where the controls are to be found and what they do in the future.
2) You didn't ask for help, you left a 2/5 review without ever contacting me. I have received lots of negative comments over the past years, especially when twitch.tv changes up something and thus breaks this extension. Your criticism certainly isn't unjustified, but I prefer to have an opportunity to fix an issue before the user leaves a low rating - just like I mention in the description.
3) Firefox changed that last year. There has been a lot of confusion around this topic. (Site specific add-ons appear in the address bar while non-specific add-ons are part of the toolbar). There is a workaround on this extension's GitHub repository available. And this is, in deed, unique to Firefox. If you know better, feel free to contribute to the extension via GitHub by either pointing to the corresponding docs, explaining how to alter the manifest or, even better, solve it and create a pull request. This is a free open source project, any help is welcome.