I didn’t find PR4’s “XD2” denoising algorithm enough of an improvement to go that route for most photos. I will occasionally use PR4’s XD2 for specific cases when I am trying to “rescue” a troublesome photo.
But…
Since PL7 applies the denoising algorithm on export, you do not have the benefit of the “clean” file when making any other adjustments. For extremely underexposed and noisy files I find it easier work from a clean “DNG” to complete the other adjustments, particularly color. I then copy the adjustments back to the RAW file and delete the DNG to reduce clutter/size in my files. I do this all with PL7.
Note: I learned this technique from @joanna so surprised she didn’t mention it.
https://forum.dxo.com/t/workflow-integrating-topaz-denoise-ai/38349/12