In the WinMX Peer Network settings yes you are correct, those values are for the amount of Allocated Bandwidth you will give to the Network. This is usually set at
7 KB/s out and 10.5 KB/s IN
Meaning your going to connect to 7 other primaries and allow around 10 secondaries to connect to you. The higher these values the higher those numbers at the top of your WinMX. This setting will also increase your speeds.
P=7 S=10 spm= searches per minute running through you and will vary.
The best settings are usually around
9 KB/s Out and 13.5 KB/s IN
This combo is a good balance between what you give and get from the network.
The Search Thread Priority is recommeded to stay at IDLE
The Search Thread Duty Cycle is set at 80% by default and usually lowering this to 40% will use less of your computers resources.
I think that covers your questions but if not as always just ask ...