Looks tight. I absolutely adore those cables. Amazingly flexible, clean, and fast.

1. Modem >>> ROUTER first. United the modem in your diagram is a router combo unit.

2. I need to read more about your post in a bit.

I did similar, but I got a DC UPS and it's running: 2 Odroids (like Raspberry pi), a wired router, and a 16 port switch. (edit: as seen here https://ibb.co/album/Jxrb06 )

TalentCell Mini UPS Uninterrupted... https://www.amazon.com/dp/B07WLD32RP?ref=ppx_pop_mob_ap_share

I would step out of the USB / PC realm and look just at DC power supplies. Like this guitar DC/Barrel power source: https://www.amazon.com/Donner-Guitar-Supply-Isolated-Output/dp/B00WHLLDWO/

NOTE: I just google for "Multi DC power supply" and found that. Point being. I have zero experience with that power supply, but DC power has been around WAY long than USB and it is very well supported across many industries. When it comes to DC, you really only need to look at the Volts too, forget the Amps. I'd say only the Beelink needs to be considered in Watts everything else just V's.