Hello friends
After a while away, I return with some news and adding some information to this thread.
Many of you do not yet have a Native NVRAM like me on your Z390 motherboards and must use EmuVariableUefi.efi for this Emulated functions.
According to my research and testing some EFI Folders of users with this same Motherboard, it seems that a very complete DSDT makes the real difference.
My Motherboard may be an exception and I really have a factory-native NVRAM, I'm not afraid to always update to the last BIOS, nothing breaks when doing so.
My DSDT is complicated and very personalized with my hardware, but someone else can patch your DSDT and try.