Vital signs of unfamiliar software are present in safe mode: TopBuzz in Galaxy Note8
I have a Samsung Galaxy S8 and have the same problem as you with TopBuzz showing up in the storage clean but unable to find it anywhere in my phone. 

I tried the SD Maid app but that did not help. However, I did try Clean Master which I have used in the past with my old phones becuse it does work better than the built in storage clean (but uninstall it when im done with it because im sure that it slows down the phone to make you use it from time to time) and that appears to have fixed the problem.

I ran Clean Master, then ran the system storage clean and did not see TopBuzz, ran Clean Master again for good measure and then uninstalled it. It has only been a few hours but I have ran the storage clean a couple times and have not seen TopBuzz at all. If you still have this problem try this out and let me know how it goes!