My understanding is each motherboard company uses its own terms and proceedures.
The ACC feature may be the unlocking, with multiplier settings in the bios?
Just learning this on another board. But..
Unlocking may or not give you another stable core. Be prepared to stress test before using with confidence. Odds are about 50/50 maybe 60/40 in favor.
For overclocking three cores will overclock higher than four.
You will need to decide whether four cores or the highest overclock is more important to you. Again you will need to stress test stability before you can depend on results.
Usually, overclocking is incremental as you discover the particular combination that best "fits" your CPU.