Important: The setting MUST be applied before mining starts or the value won't change. Even if I closed the miner and tried to apply the setting, it would not take. However, applying via .bat after reboot before the miner started worked great.
This is not true. AMD driver 19.4.3. I change REF on my RX 580 cards during mining and it applyies and changing the mining speed.
Once I got the new Win10 update, I could no longer change the timings on the fly with Claymore running. Even with the 19.4.3 driver. I tried all of the recent drivers I could find.