I advise you to upgrade to BIOS version F13 (F14a is beta). The problem is not in memory most likely. The only problem that the non-standard memory of Imac 19.1 (2666) is to double-click the mouse or keyboard to leave Sleep mode.
Btw, this EFI developed by me with the help of colleagues works properly in the F13 version of the BIOS. That's because it incorporates 300 series RTC patch after the F10 Bios update. You can also go back to Clover if you don't feel safe to update the BIOS. But I assure you that it is a simple and painless process.
If the problem persists after the procedure I will need your boot log.
Source:
https://dortania.github.io/OpenCore-Install-Guide/config.plist/coffee-lake.html#acpi