If your looking for faster rolling tires the width is not the issue, its more to do with the sidewall casing and tread compound the manufacturer chooses. Vittoria Rando Hypers are one of the faster rolling tires in a 35mm, but the fastest I've found is the Grand Bois Extra Léger Tires in 32mm. These are in clincher not tubular and of course tread or no tread does not affect rolling resistance unless its a cross type tire.
Depending on how big a Clyde you are will determine how wide a tire you need. You can probably ride a 23 pumped up to 200psi but the wider 42mm tire will be much more comfortable at 35 psi. And again width vs a fast tire are different issues. One is for comfort and one is for speed. You need to find a good comprise between the two.