Look at the suggestions I made in my previous post. These are some of the most HQ denoisers available. You can test them, tweak the settings (more than only strenght/sigma) and you'll find which is the one you prefer. The default settings are not a good reference point when you're removing noise/grain.
btw, the full power of TemporalDegrain() can only be seen when you have an optimal pre-denoised reference clip (FFT3Dfilter is very useful for that since you can specify a different denoising strenght on 4 frequency ranges)
Here is one of the first post I made on this forum that talks about the issue/solution (and I guess the whole thread will be interesting for you).