I tried again to achieve a lower voltage without losing performance. I decided to check if the same behavior occurs when changing Lite Load Calibration in the newest BIOS. And yes, it's the same. When I lower the mode level, the voltage and performance go down. But just like in the previous version of the BIOS, when the mode 1 is selected, the voltage is lower, and the performance is the same as at the stock settings. But unfortunately it's unstable (just like in the previous BIOS version) and I immediately get a BSoD when running the Prime95 small FFTs test. I tried add a positive offset in order to make the system stable. But again the offset is useless. I was still getting BSoD even with +0.04. Then I tried to change the Line Load Calibration and found that at mode 6 there is no more BSoDs during the test. And at the same time, I still have lower voltage, temperature and consumption.
Conclusion: offset is useless, only Lite Load Calibration mode 1 helps. It seems to me that it is made on purpose that if the locked CPU receives less voltage, then the performance decreases. And maybe activating the Lite Load Calibration mode 1 disables this limitation.