Ktorrent/advanced

Performance
You can configure some advanced options such as memory usage, interface refresh time, data verification options while uploading, and the type of service field for networking.

In the first row, the setting for memory assignment has options for low, medium, and high. These settings are profiles for how much RAM should be assigned for torrents as they download. It is generally safe to say most users with 512MB RAM will want to set this to medium or high, and users with more than 512MB RAM will want to set it to high. Higher memory usage will help when the chunk size of a torrent is 2MB and higher.

Interface refresh time is to configure how many milliseconds KTorrent should wait before it refreshes the statics display.

Data Checking
Data checking allows you to configure extra functionality which most other BitTorrent clients do not have. This functionality can be best described as an alternative to automated full rehashes on data when a download completes. It was introduced to KTorrent to allow the user to verify the data after a download completes, while trying to avoid the CPU intensive task a normal rehash on data takes. Basically, this feature will continuously verify every chunk a leecher requests on a torrent in uploading mode. Then if a chunk fails the hash verification test, it will be dropped and the torrent will revert to downloading mode to replace the corrupt data. It is recommended to use this feature, because it will continuously try to prevent uploading any bogus data into swarm.

The option Do a data integrity check after x corrupted chunks is an extra function on top of the normal data checking during upload mode. It is there if you want more aggressive prevention of uploading of bogus data.

Networking
I honestly don't know what to tell users about TOS guys, so this i will leave for you.

"Maximum number of connection setups:" identifies ??? and if set too high will bog down other traffic if your router can not handle the number of concurrent open connections it creates. If you are having general performance issues, try setting this number to "10."