Photo editing

Which version of Photos are you using? My screenshot is from Photos 3.0 on macOS 10.13.4 High Sierra. The rôle of the three sliders is explained here: https://support.apple.com/en-gb/guide/photos/sharpen-a-photo-phtba5e3cf7d/mac

The middle slider "edges" is important to define, what will be sharpened. If you want to sharpen only the prominent edges in the photo keep this slider to the left. If you want to sharpen small details like the eyes, move the slider completely to the right. But then even the texture will be sharpened and the image will look unnatural.

Are you saying, that you are seeing no change at all, even with all three sliders maxed out? And with noise reduction turned off? Noise reduction is smoothing the image and will make the small details less sharp.

The effects are subtle, when you apply noise reduction or sharpening.

Have you used the automatic mode or adjusted the sliders to the maximum effect? To see the sliders for the advanced controls, click the disclosure triangles to the left of the name of the adjustment.

When I set the sharpening sliders to the maximum values, the sharpening of the edges is very strong. You can see it, when you zoom in on a strong edge and toggle between the original and the adjusted image. The edge will be emphasized by darker and lighter lines along the edge.

The noise reduction at full strength is also visible when you zoom in. You will see much smoother regions.

But when you use noise reduction and sharpening together, they might cancel each other out, because the noise reduction is blurring the image slightly and sharpening can make the noise worse.

For example:

I zoomed in onto a vertical edge after applying the sharpening as shown above.

Sharpening has made the vertical edge brighter to the right and darker to the left, so it is very prominent.

I prefer to use the Definition adjustment to make the images appear sharper. It will make the image look sharper increasing the contrast without incresing the saturation too much.