Think I may be able to help as been upgrading and playing with settings on my Corebook X. Firstly usb-c is not eneabled in bios by default. For full usb-c mode you will have to activate in the bios. This will allow use of usb-c hdmi out. The I5 processor may be old but actually is a very capable one as it has the Iris 650 gfx inside. This is actually one of the best system on a chip gfx solutions out there. I have been able to play smoothly (so 45fps or above) the following games on it.
Bioshock 1 smooth on high settings
Bioshock 2 smooth on high settings
2 point hospital smooth on highest settings
Crossout smooth on low settings
Railway empire smooth on highest settings
Fallout new vegas smooth on highest settings (surprised at that one)
Now the downside. Battery on standard video playback got 4 hours 40 minutes playback streaming from prime.
Playing 2 point hospital battery was empty in under an hour.
Web browsing with mixed usage pattern about 4-5 hours mixed.
The Corebrook X does not support charging from its usb-C I have tried at least 4 different usb chargers and none worked. This included fast chargers pd 2.0 compatible.
And to be helpful I have stripped down my corebook x to see what is inside for others. Firstly internal ssd is a sata m.2 made by Kingston. Quite a reliable all purpose ssd not the fastest but when your stuck on sata mode you get what you get.
Ram chips are soldered onto the board and are of the more square type chips similar to the samsung chips however there are no obvious markings to tell the brand of them.
However the io chip is one of these ITE IT8987E and can be clearly seen mid board.
I have tested the 2 m.2 slots for compatibility and the internal m.2 slot is not capable of nvme I have tried various configs and modules but it will only accept a sata in this port. However the external port will accept an NVMe and increases the speed to around 1800mb per second The drive is rated to 3600mb per second so as there are no drivers in windows 10 specifically loaded for the nvme controller knowing the NVMe controller may help on the driver side.
You can run 2 sata based drives with no problems but if you choose an NVMe i suggest you remove the internal module as there appears to be conflict if an NVMe and sata are active at the same time.
Bios is an old style american megatrends type so nice and easy to navigate if your used to them.
And for those who wonder what it all looks like in there.
For compatibility I used a WD Black sn750 NVMe and it works great.
For an ssd test i added a Crucial MX500 sata drive and also worked great.
Hope this all helped you