Kernels in general can be ran three ways...
Used to overclock the device which is poor battery life.
Ran at normal CPU stock settings like 100-1000 Mhz and then just take advantage of the built in kernel features like Voodoo Control for better color & sound and other various tweaks thrown in depending on the device and what the dev has put in place.
Used to underclock and undervolt your device (best battery)
This last option normally people will set their device using apps like setCPU, Voltage Control or NSTools from the Market to run at 100-800 mhz which is just a tad under stock settings but gives that boost in battery life. Throw in things like taking the stock voltage settings per Mhz frequency and slowly under volting them by 15/25/50 % increments to again save more battery.
You then have different governor settings which is basically preset profile setups for different styles of activity... Most common are Lazy or On Demand but to each their own.
Playing with your kernel settings can be frustrating at times... You can and will have lockups as you explore different settings until you find that sweet spot your device runs good with. No two phones react the same so just because me and the next 20 people say hey use this particular setting doesn't mean it will work for you. Its just the varying tolerances of our processors and how they handle things...
Good area to play with is the 100-800 Mhz and try different governors and see what works good. If it remains stable for a while with no lockups then you can explore bumping the voltage down and see how it reacts. Pay attention to the threads on your kernel of choice and see what the general settings people use and go from there... Its a lot of trial and error.
Good luck and have fun
Edit: Last but most important... Don't pay any attention to benchmarks or benchmarking apps... Those are just for bragging rights and any kernel dev or experienced ROM/kernel user will tell you it all comes down to real world performance. If your happy with the device and how it runs it doesn't matter what the scores say.