You can remove the ID for specific pages if you wanted to do that, but you cannot remove them for pages in general. For example, if you wanted to add a FURL without an ID to a specific topic you would be able to do that, but you cant automatically make one for every topic that is created. This is because the ID is required to identify that item.
With regard variables, you wil be able to see the variables that are being used by the current furls as an example of what can be used. So for example if you edit the one for the forum links, you will see
forum/{#id}-{?}
The ? is always the position of variable that do not appear in the real URL. In this case the forum name, but it could be the topic name in a topic link for example. The #id of course is the ID.
There is no list available as such