When you change the blade chords on a prop with all else held fixed, the primary effect is to change the blade Cl. Wide chords produce low blade Cl's, and narrow blades produce high blade Cl's. Neither extreme is efficient. For best efficiency you want to operate somewhere in between, at the blade aifoil's best L/D point. This is in the range Cl = 0.4 - 0.7 for typical blade airfoils. Standard propeller design algorithms determine the blade chords required to achieve a specified blade Cl. There's one on Martin Hepperle's site.

There are a few approximate chord-scaling rules of thumb which are useful when sizing props:

chord ~ 1/Cl
chord ~ 1/rpm^2
chord ~ 1/diameter^3

Note the very large influence of the diameter. If you increase the diameter by 10%, the chords want to shrink by a factor of 1/1.1^3 = 0.75, or 25% narrower. The influence of pitch is implied by the dependence on rpm. Say you increase the pitch such that the rpm gets smaller by 10% (factor of 0.9). The chords then want to increase by a factor of 1/0.9^2 = 1.23, or 23% more. So bigger pitch demands wider blades and vice versa.