Persistent White Wallpaper, Performance Bottlenecks, and Brightness Key Issues on HP Elitebook 840 g3

Hey everyone, I've recently upgraded to Sonoma on my HP Elitebook 840 g3 and I'm running into a few problems:

• I'm experiencing a persistent white wallpaper issue. I suspect it's a graphics-related bug, but I haven't been able to pinpoint the exact cause. It's strange because sometimes after a reboot, the screensaver displays a background image, and when I log in, the desktop briefly shows the background before reverting to white.
• The overall system performance seems to have taken a hit. I'm wondering if anyone has any suggestions for improving performance or specific kexts I should look into. I think resolving the performance issues might also address the wallpaper problem.

https://preview.redd.it/pkjjief5o4id1.png?width=1920&format=png&auto=webp&s=7a4d7e12b9a40091f0e62c7565f1210b1abaf8cd

• Despite having BrightnessKeys and Whatevergreen installed, my brightness keys are not functioning as expected. Any ideas on what might be causing this?

Thanks for any help you can provide.

sonoma: 14.5