I've tested more, and VCCSA=0.9000v didn't reduce the vCore for 4.2Ghz, it still needs the same old 1.172v. I'm still testing, but somehow, it effects only my low-volts/speed setup (4 - 4.1GHz).

I've been running with CPU PLL=1.71v for a while now. The system is doing good, and it reduces some heat.
VCCIO seams to be important for high-speed RAM, which i don't have. But a small increase seams to be helping the PCIe/GPU too.
Command rate 1T gives better performance and most sticks should be able to use it.