CPU Overclocking Dilemma

I've been asking a tonne of stuff on and off regarding the Overclocking of my 2700k. I'm pretty late to the party so I was very lost, and to a smaller degree I still am. I know a lot more though, thanks to a few very helpful folks on these forums. Anyway, I temporarily Overclocked via Turbo Multiplier to 4.2ghz briefly. It seemed stable, but I only tested it for a mere 20 minutes using custom settings for Prime95. However, I had no noticeable stability problems there. What I'm concerned is the temperature and voltage I was getting. My Bios by default (Asus UEFI) has the voltage set to Offset, on auto. This means I'm likely seeing much higher voltages which could explain my temperatures when running Prime95. When I was at 4.2ghz, I was getting pretty alarming temps. After around 20 minutes of running it, I was getting in the late 70s (Celsius). The voltage I believe was 1.228 if I remember correct. Is this high for 4.2ghz? As I said, I had and still have my voltage on auto. However, even then, I yielded better results in the Bios. According to my Bios, I was getting between 27-34c, and the voltage was staying between 1.120 and 1.130 (on stock), Overclock was around 1.150. I find this odd. Why is this temperature lower than the ones recorded with Realtemp and Coretemp? (I checked both periodically). On idle, I was getting between 40ish with the overclock. As of now, I am running on 33c on Core 0. I also don't get my stock voltage either, and the temp isn't great. I tested Prime95 blend yesterday on stock 3.5ghz (3.9ghz Turbo) and the 100% load temperature after a good 12 minutes was in the early 70s. Is it possible this is happening because of overvoltage? I also checked the voltages via CPUz and it listed 1.225-1.240v. I'm pretty...atrocious at math oddly enough. How does 1.120 or 1.228 translate to 1.20v? Is it the same thing in the former's case??

I'm very confused about offset. I want to use 4.2ghz, but I need to find out what is wrong my with voltage and the subsequent temperature before I enable those settings again.

My specs are listed in my signature, just in case.