Topaz can work as a plug-in through Lightroom. It is a suite of products. They can be viewed as performing similar functions as Photoshop/Lightroom, but often in a streamlined, and sometimes superior, approach.
I make use of 2 of their products -- Detail and DeNoise. DeNoise is noise reduction, a bit better than Photoshop/Lightroom. I sometimes use it for very high noise images -- over 12800. For moderate noise, I just use Lightroom.
Detail is excellent as bringing out the details. Ultimately similar to using sharpen masking in photoshop, but much simpler. (Uses a bunch of pre-sets, you view the before/after and pick the level of detail that you want). I find it excellent as bringing out architecture details, etc.
Each of their products does one basic task-- They have a masking product. They have a focus correction product. B&W conversion, etc.