I think the feature where to choose, which torrents you
want to download is pretty hidden!
I would recommend it, if you can choose that at the
beginning, when you add the torrent file!
Then there should be a Popup Window to choose the files
you want to download!
I uncheck the files, I don't want, press okay, and then
the download begins! (some Clients do that this way:
BitComet, Rufus etc.)