300W sounds overkill for no GPU plus there may be some modification required to fit the 300W. The 160W AC-DC should be more than adequate for no GPU system and can even support a 1060.
Check out the NFC store as Josh sells a C8 connector that will fit both the connection to the internal brick and to the mounting holes at the back of the case.
Thanks for the answer. I already have 300W unit so I'm gonna use that. 300W hdplex AC-DC does have 3 pins while C8 connector uses only 2. Won't that cause issues down the line? Especially as I plan to move around Europe, southeast Asia and god knows where else.