What's Inside the 2019 Mac Pro? Complete Disassembly and Analysis
A more detailed disassembly.
Update PCIe Expansion Cards that work in Mac Pro
So you can install an NVIDIA card (and it will work if you use Windows boot camp) now we need drivers for MacOS X
Adding additional storage
Internal Storage Options for Mac Pro – PROMISE Pegasus R4i RAID Storage MPX Module and Pegasus J2i to conveniently store and speedily access upto 32TB of data over internal buses. Available now at the Apple.com and will be available soon through the Promise global network of distributors and value-added resellers. *Additional Capacities Coming Soon.
Video from Appleinsider
With the Sonnet M.2 4x4 PCIe card installed in your Mac Pro® tower; Windows® or Linux® PC desktop or server; or Thunderbolt™ to PCIe card expansion system with an available x16 PCIe slot, you can use it for instant-access media storage or as a high-performance scratch disk. Mac® users can even install macOS® on one SSD to create an incredibly fast boot drive(2) and create a RAID 0 set with the other installed SSDs without loss of performance. However you use it, this card’s performance is impressive.
These drives will not be encrypted by Apple T2 chip.