How does the sound of the PCC88 and PCC189 compare to the 6922/6DJ8 and its iterations?

The former are also classified as 7DJ8 tubes.

Check out the issue of Vacuum Tube Valley with the overview of the 6DJ8/6922. That would be much better than relying on the all-over-the-place anecdotal reports of different users! 

Upscale sells 7DJ8, why not ask them?
https://upscaleaudio.com/collections/preamp-tubes/products/matsushita-national-pcc88-7dj8

I'm not relying on all-over-the-place anecdotal reports of different users. I'm gathering information from all sources, sifting, evaluating and noting where there is consensus and divergence. Unfortunately the sample size of user experience is smaller than I had hoped.