From what I know, Speedstep/EIST are hardware based power management functions that can ramp clock speed up or down as required. There is still OS level power management, hence what I said about changing the power plan. Again, I'll reiterate that for most people there is no benefit to running at max clocks all the time, your Windows & your CPU are pretty good at ramping up clock speed as needed.
I'm not sure if I understand the rest. Are you saying that if you lower Vcore below 1.16V your CPU isn't stable? Or are you saying that lowering the Vcore setting in the BIOS on your new mobo doesn't seem to lower the actual Vcore voltage?
As far as I know, automatic power saving features (i.e. c-states and p-states) involve adjusting voltage and frequency in tandem. In which case, if you keep frequency at max, voltage will stay at max too.
To be honest, I don't really know what the problem is here. If you want to run your CPU at 4.2+ GHz all the time, there's not really any issue if the voltage stays at 1.16V. Alternatively, just allow the various power management utilities to ramp voltage and frequency up and down as needed.