Hi everybody!
I watch a lot of videos mostly on Youtube using most of the time Firefox and sometimes Chrome as browsers.
I use a really great FIREFOX extension named "Session Manager" to save my sessions. So when I boot my computer and start Firefox all my previously opened tabs load up again. It's really great in many ways however it has one downside: you probably all know how irritating autoplay can be – you've got to frantically open your pages and tabs and physically pause each video unless you want to listen to the unholy noise produced by multiple videos all playing at the same time!
So I am looking at using some kind of STOP AUTO PLAY extension for youtube in Firefox or really ideally for the entire web (something working for any browser/any site) and I do not know which one to use.

This one looks like it may be good
However it's only for Chrome and Youtube so it's very limited.

My concern with all these STOP AUTO PLAY like extensions or Monkey Grease script is the following:

When I have found a video I like and I want to SAVE it to my computer with "Replay Media Catcher 4" and the way to do that is:
1) open "Replay Media Catcher 4"
2) click on the REC button in "Replay Media Catcher 4".
3) only then go to the webpage of the video I like
4) click on "Window Key + F5" to restart the video
5) the video plays and "Replay Media Catcher 4" starts by itself recording the video
6) Once "Replay Media Catcher 4" says "complete", click on STOP button in "Replay Media Catcher 4"

The thing I wonder about is with some extension or grease monkey script in place that stops all videos from playing, I am guessing I won't be able to do "Window Key + F5" to the video page anymore.
And in me experience, just pressing manually play on the video is not enough for "Replay Media Catcher 4" to successfully record the video. "Replay Media Catcher 4" really requires to launch the videos as it was first time watching and therefore requires to be able to launch the video doing "Window Key + F5" to the page of the video, that way "Replay Media Catcher 4" gets a clearer sense that the next video starting is to be recorded and does record it.

So I really wonder what solution to implement to stop all videos from autoplay WITHOUT creating an impossibility to REC videos with "Replay Media Catcher 4" ultimately.

Would any of you know of an easy solution that works, ideally for all browsers and all website. If you know of a solution that only works with Youtube and Firefox, I am still very much interested in hearing about it and why you think it's best.
Thanks in advance to all you guys. I very much any help with this.