Most CO2 controllers are little more than a switch, powering on or off the electronic tank regulator depending on a metered reading of CO2 concentration. It is the regulator that has a hose to deliver CO2, which is fitted straight into the unit.
AFAIK the tank pressure setting has little effect: the controller will continue to run the regulator until desired saturation level is reached. For preset controllers this will be 1,500ppm.
I've trialled with various DIY delivery systems in sealed rooms, piping the gas directly to plants, but I can't claim any benefit over fitting the hose to a fan or AC vent.