I'm having a little trouble making out what your trying to say, but I'll try my best to answer. Sounds like you're trying to understand the relationship between queues and JBoss ESB.
"...I would like to understand better the queue system that ESB provides"
ESB doesn't really provide a queue system it instead relies on underlying transports to exchange messages.
You can use JMS as the underlying transport and if you do should refer to the documentation for your messaging implementation to see how queues are managed.
As for ESB, you should probably try to think about it in more abstract terms and work your way through the quickstarts using the Programmers Guide as a reference if your just getting started.
"...Do I have to provide a queue for each "functionality"..."
You have to provide at the very least an ESB channel(which I believe is always a queue in your chosen messaging implementation). You may optionally provide a gateway channel. So if you use a JMS gateway you could end up with two queues per service.
As for performance that will depend on your implementation specifics and the underlying hardware/network topolgy, but if you're only dealing with hundreds of messages I don't think that will ever be a problem(most installs I've worked with deal with hundreds of thousands or millions of messages in reasonable time periods).
Hope this was helpful
This thread has now been moved to ESB forum.