Here a list of specs I found browsing the forum incl. source (no guarantee whatsoever though)
Memory
two (dual channel RAM - 2x16GB is faster then 1x32GB) SO-DIMM 260-Pin with 64 GB total max, supporting DDR4-2666, LPDDR3-2133 and LPDDR4-2933, no ECC support
SSD
PCIe 3.0 from that thread
Configurations 1x4, 2x2, 1x2+2x1 and 4x1
Take a look here and here for SSD speed considerations
Video
CPU supports three displays (laptop lid and two external via 1 x USB-C/DisplayPort 1.2 and 1 x HDMI 2.0)
You can look up max resolutions and refresh rates here to choose a matching monitor and where to connect it.
DisplayPort over USB-C can get a bit tricky if you use a hub since it might need to share bandwidth with a USB device connected to the hub. So if you want to connect a device using USB3 SuperSpeed to that hub you will only have two of the four DP lanes available, hence half the refresh rate or resolution. (Out of some reason you can either use 4, 2 or 1 lane - not 3 of the 4 available lanes) USB2 devices will use separate pins and shouldn’t influence video bandwidth.
Feel free to correct me or post additions.