I take it you have found and read at least part of the Dortania OpenCore guide.
There is also the essential Ryzen config.plist guide.
I have a couple of Asus B550 systems I dual boot macOS and Windows 11. So to help you I have attached an OpenCore 0.9.4 EFI for you to use, or as a base/template for your own EFI.
It contains the essential kexts, SSDT's, Drivers and Tools required for booting macOS on an AMD Asus B550 system with a 6-core CPU and Navi II discrete GPU. All you need to add to it is the SMBIOS data for a MacPro7,1 system. This goes in the PlatformInfo > Generic section of the config.plist.
You can generate a MacPro7,1 SMBIOS using Corpnewt's GenSMBIOS script, works in Windows and macOS.
You can download macOS Sonoma using Corpnewt's gibMacOS script, works in Windows and macOS.
You can edit the config.plist using Corpnewt's ProperTree Plist Editor, works in Windows and macOS.
corpnewt has 89 repositories available. Follow their code on GitHub.
github.com
Select the repository you wish to download from the page linked above.
Select the green coloured button named 'Code'.
Then select the 'Download Zip' option.
Hope this helps,