I've read a couple of times that increasing the Vertical Blanking in CRU will fix high idle VRAM clocks. Finally gotten around to test this on my G9.

The following steps are to fix the high idle VRAM clocks for the PBP mode, specifically 2x 2560x1440 @ 120 Hz:

1. Download CRU.
   
2. Important: Disable PBP
3. Run CRU.exe, at the top you have a dropdown of different displays (for me the G9 has three entries).
4. Choose the display which has an Extension block. At the bottom you'll find the Extension blocks, click Edit and then under Detailed resolutions choose the 2560x1440 @ 119.997 Hz one and then press edit once again.
   
5. Increase Vertical Blanking from default 85 to 101.
6. Repeat 4-5 for second G9 display entry.
7. Close the application (press OK for all opened windows) and reboot.
   
8. You might need to adjust re adjust resolution/refresh rate in the Windows settings.
9. Disable Record Desktop in the Radeon Settings

Here is a picture to demonstrate the steps (needs to be done for two display entries):
https://i.imgur.com/8Q2X9Lf.png

That's it. It could be for your specific graphics card a different value is needed. But the principle is the same, increase the Vertical Blanking value. I've tried up to 150, nothing broke, but I suggest in case 101 is still giving you high idle VRAM clocks to go up by 10, so 110, 120, 130... and find the right value for your config.
Tested with a 6800 XT (21.1.1) and Odyssey G9 (Firmware 1010.2) with PBP mode enabled (2x 2560x1440 @ 120 Hz).
This workaround is saving me about 30-40W in Idle and dropping temperatures by 10-15°.