Ok, maybe I'm being stupid but this is driving me crazy.

I have the plugin working fine (thanks, it's great)

but, I cannot find a list of parameters for embedding...

Ie. on the documentation page, you give an example ...

(an "autoplaying" YouTube video of 600x450 dimensions would be displayed adding this to a content item: {youtube}he73js822|600|450|1{/youtube} )

But WHERE can I find the list of all available parameters? I would like to use showinfo=0 (hide title and other info) and woudl also like to hide related videos..

Finally, I would love to be able to load it with captions automatically? Is this possible?

You cannot hide related videos cause youtube and not AllVideos generate them.
For parameters like hide title just check at AllVideos plugin settings.

You can do it relatively simple... This blog explains how, but is in dutch...

www.freelancewebdesigner.nl/joomla-extensies/49-geen-andere-videos-aan-het-einde-van-youtube.html

This can be embedded in allvideos, but i'm not sure how to make it an option...

In short.. you can do it by adding ?rel=0 to the video-id

Here is a list of YT params,

code.google.com/apis/youtube/player_parameters.html

Hope this helps!