The Git implementation done in Talend has a similar behavior as the SVN one.
All branches/tags are visible for all projects on the same Git repository. Therefore, if you create some branches/tags for one project, all other projects on the same Git repository will have the same list.
About the unlock mode: Any item modified will be kept locally, and will never be committed / pushed to the server until the item is unlocked. Project items will be stored temporarily on the stash system of Git if needed, so that they are not pushed until they are unlocked.