In my opinion it would probably be using Qubes certified hardware with Qubes on it and then routing everything through whonix VM.
Curious to know if anyone has anything else that is more secure than Qubes - I mean like does anyone know what darknet vendors use opsec wise?
Also I heard Snowden used Tails OS when blowing the whistle - so perhaps using tails would be up there.
Darknet vendors mostly use Tails, as it makes it easy to wipe any tracks. The chance that they will be targeted with malware is low, they require privacy and anonymity over security.