Here are 2 comparisons, based on the same image-crop. The image was taken on a sturdy tripod, but an aperture of f/16 was used. That narrow aperture caused diffraction blur (with resolution loss) and, additionally, a tiny bit of subject motion blur (despite my trying to shoot when the wind induced subject motion was at its minimum) was caused by the required exposure time of 1/8th of a second.
The first is a straight Raw conversion with an excellent Raw converter without any additional sharpening, with first a Sharpen mode correction and then a Stabilize mode correction applied to that crop. Here they are, side by side:
Click on the image to view it at 100% zoom, and make sure that your browser doesn’t zoom in itself. Maybe it’s better to download the image and view it in an image viewer or editor at 100% zoom setting.
Due to the softness and resolution loss caused by narrow aperture diffraction, Sharpen mode already produced a significant improvement, but removing the tiny amount of subject motion blur with Stabilize mode helped it a bit more.
The Raw converter I use also offers a feature called “Diffraction Correction”, which usually does a very good job of applying automatic Deconvolution sharpening (like the Topaz InFocus plugin does), to compensate for the diffraction blur. I also used that as a Raw conversion, again without adding any additional sharpening.
This time, the Raw converter already took care of most of the Diffraction induced blur. Therefore the subsequent Sharpen mode adjustment only produced a tiny bit of additional sharpening, as it should. By using the Stabilize mode, again a slight improvement was achieved.
This demonstrates that if an image needs more help in regaining the original sharpness, Topaz Sharpen AI will make more of a difference. If that same image is already reasonably sharp, then the gains will be relatively small.
Hope that helps.