Base model iMac Pro teardown sheds more light on its upgrade potential - 9to5Mac
Upgrade your iMac with OWC, 2017 4K Retina Edition
2017 iMac SSD upgrade & Speedtest - YouTube
How to upgrade RAM in the (Mid 2017) 5K iMac and save up to ~$900 [Video] - 9to5Mac
Surprise! The iMac Pro has Upgradable RAM and SSD - The Mac Observer
Amazon.com: PCIe NVMe Gen3x4 SSD 1TB 512GB 256GB 128GB 3D TLC NAND Flash Hard Drive SSD Replacement for Macbook Air 2013-2017, Macbook Pro Retina 2013-2015, iMac 2013-2017, Mac Pro 2013, Mac Mini 2014 (1TB) : Electronics
Upgrading a 27-inch iMac 5K to 14 terabytes - Replacing the Fusion Drive with both a SSD and an harddisk
SSD Upgrades for Apple iMac 27-Inch Late 2013 - 2019
SSD Upgrades for Apple iMac 27-Inch Late 2013 - 2019
2017 21.5-inch 4K iMac memory upgrade kit includes 32GB of RAM, tools to take it apart | AppleInsider