It's the effect of reciting the Heart Sutra. It probably depends on the denomination and the way of thinking of each monk
Disease-free health, family safety, prosperous business, longevity, safe delivery, etc.
That's probably not what we'd expect. Sutras aren't spells, are they? If there is a benefit of making such desires come true just by chanting, then all the monks must be transcendently happy and outraged.
The Buddha's teachings are explained in the sutras. So is the Heart Sutra. I'm moved by the wonderful teaching of the famous “color is the sky, the sky is color.”
So by chanting it, you, your family, and everyone around you will know the Heart Sutra. Even if you don't understand its meaning, you know it exists. I can remember it by ear.
The fact that I learned about it may unexpectedly blossom as a sign of seeking Buddhism.
When you are overwhelmed by your worries and suffering, what kind of teachings are explained in the Heart Sutra? It may be an opportunity to seek Buddhism.
There is no doubt that Buddha's teachings are explained there, and they will help save everyone from suffering.
Sorry if that wasn't the answer you expected.
However, I think there is a relaxing effect of reciting sutras at a constant rhythm. Habits may also have the effect of bringing sharpness to life.
I think that's the effect of simply chanting.