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.
Going back to the 18.9.2 driver allows me to dynamically update using AMDmemTweak again while Claymore 11.9 is running under the newest Win10. 19.6.3 still didn't work. It took quite a while to crawl back to 18.9.2 to find one that worked.
EDIT:
Well, I spoke too soon. I was able to do it briefly but then it locked me out again. I don't know what the solution is other than making sure to modify before running Claymore. But it sure was nice for a while to be able to bring up the GUI version and modify timings on the fly while Claymore was running to see the effect.