Not entirely, Topaz is now pushing their new Topaz Studio which is a stand alone tool that includes some cut down form of all their plugins, which together give most of the tools that photographers commonly go to Photoshop for, and they have said they will be progressively adding missing features as part of Topaz studio.
Topaz Studio with basic capability is free, so you can download and try it. You then pay for more advanced capability as you feel the need.
Topaz studio also works as a plugin for Photoshop and Lightroom, and it seems that the current Topaz plugins will probably fade away, as Topaz have said that the multiple plug in approach was impossible for them to manage. It was also confusing for the user.
It's still all a bit complicated at the moment, with some features in Topaz studio more powerful than the plugins, and some plugins more powerful than the equivalent Topaz studio capability. But, you can also run all the original Photoshop Plugins as Plugins for topaz studio.
I would ignore the original plugins, and download the free Topaz studio, and use that as a starting point to give it a try and learn what its capable of.
Cheers,
Graham