Probably much less... I think!
The relay board: less than 500mA when all of the 16 relays are activated (which will never happen),
One or two 12V PC fans, which require 700mA each.
The Arduino Mega (and touchscreen): No idea yet, but I doubt it's more than 500mA
The few sensors: No idea yet, but again, I doubt it's more than 500mA
I don't need to power powerful motors or things like that directly from those power supplies, the heavy loads will be connected to the 230VAC through the relays.
I can't tell exactly now because I (still) haven't received any of my things yet, but I think I'm far from 2A that those adjustable modules will provide safely, and overall far from the 5A of the 12V power supply...I hope I'm right.