Thanks a bunch
@msystems for pointing me into the right direction!
I now understand better your statement specifying the SlimQ having a DC barrel output.
After some browsing looking for your proposals, I saw you and others already had interesting talks about that here in the forum:
(What a letter soup... Heh.) The USB Power Delivery Revision 3.1 specification enables delivering up to 240W (48V at 5A) over a Type-C cable, so I was wondering: are there any USB-powered picoPSU/DC-ATX units available on the market? Methinks it is time to get over the brick and the barrel.
smallformfactor.net
Since I want a brickless build, such a cable is not really suitable. But as one could be handy for some early testing, I still checked what was available.
One corresponding cable was linked in the thread above, but is 12V only.
After some digging, I've found this one which is up to 20V / 5A / 100W:
With the 120W Xiaomi GaN charger in mind, I thought the 100W max was too low.
So I've then stumbled upon this Xiwai cable, 20V / 7A / 140W:
Find many great new & used options and get the best deals for xiwai USB-C Type C Input to DC 5521/5525MM Output 20V Power 140W Charging Cable at the best online prices at eBay! Free shipping for many products!
www.ebay.com
But as you can see in the picture above, they say:
Output: DC5.5mm male, DC20V 7A 140W Max.(Also support 135w/100w/65w power output).
No mention of 120W as an output power, which would correspond to the 6A delivered by the Xiaomi charger.
Hopefully that's not an issue?
Here I've found lots of these tiny PCB units, such as this one:
But as it seems to be the case for all of these boards, the max supported current is 5A.
No luck in finding a unit dealing with 6A or more.
Would that mean the choice of a 20V GaN charger is limited to 100W max?
To resume, am I right thinking there are the following options?
1) Limiting the power needs in the X300 BIOS to not go beyond 100W, and go with a 100W GaN charger along with a 20V 5A trigger board
2) Get a 120+W GaN charger with a cable such as the Xiwai mentioned above
3) Use a SlimQ 150W