More open descriptors for anything means more open sessions, more resources in use, more memory, more shared usage of the CPU. Therefore the more RAM you have and the faster CPU you have, the better.
I'm not sure, my experience with the limitations on open file descriptors may be out of date, I thought the maximum used to be 65535 per process.
My understanding is that the apache webserver works better with more file descriptors and their server apparently tries to increase the amount of allowed descriptors when it interacts with the operating system. I think you'd see errors that you've run out of descriptors which indicates that your system limits should be altered, if possible, to help the server's performance.
Sorry, that's not probably exactly what you were looking for. There are likely wiki's on the Apache webserver and how to tune it for better performance.