Please correct me if I'm wrong, but so far I was under the impression that setting 'KeepAlive' to Off will render 'KeepAliveTimeout ' and 'MaxKeepAliveRequests' values irrelevant. Based on this assumption only the 'Timeout' setting would have any effect on performance.
Timeout is sometimes a problem with web scripts that need a long time to finish (uploading large amounts of bibliographic data with immediate dataprocessing, for example) - Apache will kill them off unfinished, even if repeated requests are made by the script to extend the timeout value (requests not granted, I guess). Large timeout values are only a problem with bad scripts (endless loops, etc), otherwise a correctly terminating script with a short runtime will not cause performance problems.
Debian