HI Dan, thanks for your informative posts! I was reading specs on Everymac.com and it lists the 2017 27" iMac OEM SSD in the Primary Storage position (SATA) with the PCIe slot empty (secondary). But from your post it sounds like the opposite, the SSD come in the form of a PCIe "blade" with the SATA slot empty?
any clarification would be helpful, as Im buying a used 2017 iMac 27" 5K and I'd like to upgrade to two internal SSDs, 1st for OS/apps, 2nd for files. And it sounds like getting an OEM 256G blade would be difficult to say the least. (yes I aware of Ext SSD option/warranty/teardown/etc but I need both T3 ports for audio hardware)
many thanks