> I don't know of any tracker that will tell you what IPs are currently connected
Maybe I don't fully understand your comment but every tracker will tell you what IPs are currently connected. That is what trackers do, that is the very feature that make them trackers.
Sorry, my brain made the connection from the previous sentence between "before you begin to download" to "telling you the IPs". I should have added that to the sentence that confused you as well, I haven't seen any that tell you the IPs that are currently connected before you begin to download. So you have to initiate the download before you can find out who is connected.
Maybe I don't fully understand your comment but every tracker will tell you what IPs are currently connected. That is what trackers do, that is the very feature that make them trackers.