ok im wondering which one i should be using...
i got cpufreq running on demand. but i now see an option in my kde control panel where i can let acpid handel cpu throttling. i have both turned on atm. should i change that?
You don't need both of these. All cpufreq really does is set the governor, minimum and maximum clock speeds at boot. Once this is done, the governor itself (in the kernel) handles CPU frequency. If you don't want to ever change the governor, then cpufreq is probably all you need. If you want the governor to depend on AC/battery operation or something else, then probably you will want to use KDE's option, assuming it provides finer control over the CPU frequency.
For example, I use acpid to switch between the ondemand governor for AC and the conservative governor for battery operation.
Hope this helps.