The EFI contents look OK for a Coffee Lake (CFL) system.
I have cleaned up your config.plist, removing a number of unnecessary entries, so it is easier to read and navigate.
Your USBPorts.kext is looking a bit on the light side, as it only activates 11 x USB ports. You could activate another 4 x ports, if you wanted.
You have two entries for the built-in Realtek Audio device, one in the DeviceProperties and the other in the boot args. I have deleted the DeviceProperties entry, as the boot args entry takes precedence and the other just look wrong.
I Enabled Misc > Debug > DisableWatchDog entry.
Assume you don't have a WiFi/BT card installed in your system, as you are not using any WiFi or BT kexts.
Try this cleaned up EFI/config.plist and see if it helps. Just add your iMac19,1 SMBIOS data to the config.plist, don't change anything else.