I am using Denoise AI and Sharpen AI and they are both excellent. Recently it has mainly been Butteflies and other insects though I have used on a face as well. They have added masking now so you can select the areas you want to Denoise or sharpen but have not really found this necessary. There is often a tendency to over sharpen, In our Camera club training, we always suggest using the amount sliders until it looks about right then backing off by about 30% and that will turn out about right else it will look over sharpened. I am finding that Topaz seems to hit that just about right in that it sharpens enough without over sharpening. I tend to set the Sharpness setting between 50 and 60. Also remember that Sharpen AI can deal with movement as well as focusing issues. Are you using the current version as it has upgraded several times in the last few weeks.
Dave