Unfortunately, what all this means is there isn’t a ‘one size fits all’ solution (in both the literal and metaphorical sense) to the question of tyre pressure and width. 

Wide tyres run at the same pressure as narrower tyres will have a low rolling resistance for said pressure, and offer the added bonus of greater comfort too. On the other hand, narrow tyres at high pressure have the added bonus of having lower overall drag at high speeds than wider tyres and have the bonus of requiring less energy to accelerate as they lower the rotating mass of the wheels.

What it means is both can have a place depending on the goals you wish to achieve. If you’re in a tight circuit crit race run on relatively smooth surfaces, you might want the lower weight of narrower tyres. But if you’re out training, especially on poorly surfaced country roads, the added comfort of wider tyres and the lower rolling resistance over the course of a long ride might be what you’re looking for.