- Yes, you have to install the extension. Does it increase fingerprint? Not sure if use of the extension gets reported or can be collected.
- You have an opportunity to associate web sites with certain containers. If you open a bunch of bookmarks that are in containers, they will open up as you configured them.
I think that is your question on #2.
Right clicking a URL adds a context menu to open that link in any of your current containers.
Install the addon and try it out.