Not to sound like a total jerk, but here is my standard lecture:
You should have looked this up BEFORE you rooted. Rooting plays with system level necessary files, and doing it is not an action to be taken lightly. I know it is easy with the great devs we have, but that does not change how serious it is. This type of research should have been before rooting, as now you have a phone with no warranty that you have no idea what to do with. If you did not see a clear reason to root, why even bother? Again, there is a serious chance (small, but serious) of bricking your device, so rooting should be well researched--you should know what is going and the repercussions on on at least a basic conceptual level. I am not saying you should know everything (questions are always welcome on these forums), but what you did is akin to buying a boat, going straight out into the water, and then realizing you should probably get your license so that you can learn how to turn.
Now, the help:
Flashing kernels does not require a wipe (it is a good idea to wipe cache, but that is not something you would notice--it will just rebuild). Kernels can be undervolted to give you better battery life, overclocked for performance, or both.
Apps like SetCPU can play with frequencies, too. This will not undervolt, though.
Wireless Tether will give free wifi tethering pasts May 15.
various tweaks like LCD density in the build.prop can be done.
I would suggest buying Titanium Backup. It makes wiping a breeze, as within the hour all of your apps are back up and running with all data restored. After you do that, I would strongly suggest your try different ROMs, as that is a major reason for rooting.
Also, MAKE AN NANDROID!
-Nkk