This is incorrect. bittorrent is a protocol. The number of queues and their priority is something which is client dependent. The clients may contain code which lowers their upload priority to other clients who are not sharing (leech only mode) either wilfully or because their communication control port is blocked.
No there are many queues. The remote p2p client may be sharing many other files and the sharing of those other files may be set at a much higher priority than the one you are trying to get. Also some clients allow setting a maximum number of connections per torrent. So if remote p2p client is already sharing with say 4 others, and has a maximum of 4 clients set, you will just have to wait until one of those other 4 drops off before you can download from that particular remote p2p client.
p2p is all about sharing which means both uploading (seeding) and downloading (leeching). If other people were not prepared to share, you would not be able to download anything, so it is only fair and proper for you to be connectable and share what you have downloaded with others who are trying to download.
You do not have to use uPnP in order to turn on random port feature. What you do have to do is to set a limit on the random port range and then use that random port range (external port start through external port end to forward to internal port start through internal port end) in your port forwarding on the router.
So do not use the default - pick something else. Security by obscurity must never be relied upon, but it does not hurt.
Also something else which should have been emphasized -- do not run a p2p client from your own userid.
Create a separate user p2p with its own password and home directory etc and run any p2p client solely under that user account.
NEVER EVER, EVER run p2p client as root, because it is not just a client but is a daemon as well, and daemons with bugs are ways of compromising (ie cracking into) a system.
(And on distributions which have sudo facilities, ensure that the p2p account cannot sudo to anything.)