So assuming you have something like an H80 or H100, or one of the many other brands that do basically that same thing. That's good for a decent OC. My best guess would be that you could lower that voltage while keeping your OC at 4.2. You would have to use trial and error, lower it a little and stability test it, rinse and repeat until you find the lowest possible voltage that keeps it stable at that OC. This would lower your temps.
Also, of course you could keep the voltage at 1.225 and ratchet the multiplier up one step at a time....stability test and watch your temps....until you find how high you can get while keeping the temp at an acceptable level. I always aimed to keep mine around 80C maxed in Prime95 Small FFT. This leaves a lot of thermal headroom because no game or regular use will stress a CPU the way Prime does.
Thanks again a bunch for the info!
I might have some more questions for you all tomorrow, if I poke around in the BIOS some more. The only thing I've done so far is use ASUS one-click automatic OC setting... the "CPU Level Up" to 4.2 ghz
After that I only manually lowered the Voltage, because the default Level Up setting for 4.2 ghz was really high at 1.28v