Stock fuel pressure regulator usually means higher base fuel pressure sure to fuel overrun (reg not able return fuel sufficiently at idle). So yes you can reduce your duty at idle to compensate but by reducing your injector duty you may be sacrificing idle quality. Ideally with idle, you want low pressure and higher duty. This will give you overall better idle characteristics.
Think of it as a garden tap with huge pressure behind it. As soon as you open the tap, water shoots out excessively. So to full your bucket you need to turn it on and let it dribble out otherwise it might splash and fill the bucket too quickly. So the water flow may be very rough and inconsistent.
But if your tap had lower pressure, you could open your tap a few turns and leave it there until the bucket fills up. With a nice even pretty flow of water.
Similar to the stock tb / stock intake manifold / stock valves / stock cams comments. You can make big power on all the above but you can make more effectively with the correct component. Correct meaning made for the application.