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

I recommend getting a copy of Vacuum Tube Valley issue 7. They test and report on a wide variety of these frame-grid tubes! And are trustworthy! BTW, I have at least two preamps that use these tubes - an ARC SP6 and a Conrad Johnson PV3. Hence my interest.

Great reference. Thank you!

This is a good source of info: https://www.audioasylum.com/scripts/d.pl?audio/faq/joes-tubes.html

Alas, Joe has nothing to say about the tubes I'm inquiring about.

Sorry about that ! Brent Jesse Tubes lists and mentions them in the descriptions of tubes.