I'll be porting my Mac from Yosemite to High Sierra and will follow this thread with great interest! I'll be setting up a 4x SSD = 2.5TB on my 2x PCIe Apricorn Velocity DUOs in RAID0.
Yes, use the RAID assistant in disk utility. I was able to set it up in an earlier Beta. But I think this is not fully baked as I just tried creating a RAID 0 and got errors. Tried RAID 1 and got more errors.