I recently tried the heavily promoted Topaz Sharpen AI product. I had previously tried a product by a different company called DXO that was supposed to be an improved RAW file processor, supposedly because it knew more about individual cameras and lenses than Photoshop. And because it used 'AI', or artificial intelligence. The product often processed RAW files differently than Photoshop, possibly with more noise removal. But overall I didn't buy the premise about the product, and didn't think it offered anything that couldn't be done with Photoshop. And I think they are using the term 'AI' very loosely.
So for this reason I perhaps tried the Topaz Sharpen AI product later than I should have. I was mostly using Photoshop's "Smart Sharpen", which is not bad. I think in this day and age of low resolution internet photos, not many people are looking at the actual pixels of their photos. But I still do, and in fact it is the first thing I look at. If an image is not tack sharp, I throw it away, no matter how good it might look in a Facebook post.
Sharpen AI can sharpen photos that are out of focus, have motion blur, have high ISO, were not focused well, or were taken with suboptimal equipment. You can select between 10 different sharpening modes, or let the application auto chose the best one. You can not specify a percentage level of sharpening. Noise removal is done with sharpening, and Sharpen AI always leaves you with a totally noiseless background (which you might find fake looking). So you don't necessarily need the Topaz Noise Removal product, but if you are someone who uses high ISO's, you might have more options by separating the noise removal and sharpening functionality.
Topaz Sharpen AI can be used standalone or inside Photoshop as a filter. For me the latter option is easiest. Sharpen AI seems to occasionally have problems with RAW files, so you should process your file first and convert it to a JPEG before passing it along.
A few times the final result saw so sharp that I upscaled the photo (made it a higher resolution). Topaz has a product for upscaling while preserving detail as well, called Gigapixel AI. Photoshop has similar functionality in the "Image Size" function that may be comparable, but I suspect Topaz is better. For sharpening, Photoshop, even with "Smart Sharpen", can't compete with Topaz. Topaz's ability to separate noise from detail and then enhance that detail without creating artifacts is just uncanny.
Until about seven years ago I was using a 300mm f2.8 lens and a 2x teleconverter, and even though I used a tripod, this combination didn't quite give the sharpness I later saw with a 500mm lens and a 1.4x teleconverter. So now I a going back over a few thousand photos... The two examples, a Black-backed Thornbill and a Cloud-forest Pygmy Owl, were photographed with the old lens combination. The owl was not that bad, but there are few photos that don't have room for improvement.
The real strength of this product may be in taking bad photos and turning them into much better photos. That is not something I am interested in, but there are examples of this on the Topaz website.
Also check out Topaz's products for enhancing videos. Here is a link to Topaz Labs.