After doing some tests with SMBIOS MacPro, iMacPro and iMac18,3, I am now a happy camper with SMBIOS iMacPro1,1.
Logic Pro X seems more optimized with the iMacPro1,1. The CPU usage is more spread between the cores and threads and playing softsynths seems like a breeze and CPU usage is quite low (Alchemy) compared to SMBIOS MacPro where 1 thread (the last one) is pretty high CPU usage. After running and testing with iMacPro1,1 for a few hours, I can safely say that I am more than happy running this system, and this is the best system one can have for a DAW.