The Nas hardware is complete for now.
Added 2 G.Skill sticks, a Quadro P400 GPU for transcoding and a XPX SX8200 M.2 i had lying around.
I also had to buy a new PSU,the Silverstone ST30SF.
It seems i damaged the old one by connecting the 24pin ATX and the 4Pin Cpu cable at the same time. Even though its kinda standard and it was also working that way with a Flex PSU.
However the manual stated that the 4Pin should only connect when not using 24Pin. Thats weird. Using only 24pin now.
The minimum idle power draw is around 31 Watts. Thats almost the same as before. It is possible that i swap that out at a later stage. I own a 80 PLUS Gold SFX PSU which is currently in use.
The Delock Sff cable also arrived and they are really cool in comparison to Sata cables. I only have to route one single cable to the Disks.
The USB situation was also solved with this internal Adapter from Amazon. I might split the cable later aswell to make use of the front USB-C port but realistically i probably will never use it on a NAS. So USB-A it is for now.