As example with Teamspeak in background, moving the mouse quickly in the CSGO menu I already noticed FPS drop:

50fps moving quickly the mouse in the menu (fps_max_menu = 120)
I investigated using https://rzr.to/pollingrate from Razer. The results confirmed my first impression:

Polling rate drop with Teamspeak opened
For my first attempt I changed some BIOS configuration. I set the RAM settings to use the XMP profile.

Small improvements but still not perfect...
Then I used a polling rate of 4kHz for some days. CSGO was stable and my FPS were good. Even the polling rate was stable:

Stable FPS with a Polling rate of 4kHz
Of course when you buy an 8kHz mouse you want to use the entire performance of your device.
I remembered from my study about the IRQ interrupts. I started to read how the interrupts work in Windows 10. I learned about the Message_Signaled_Interrupts. With the tool MSI_util_v3 (thanks to this article message-signal-interrupts-yes-or-no) lists the IRQ number, the type and priority of our peripherals. I discovered that my graphic card and my audio card were using the same IRQ numbers (16). I set the graphic card to use the "msi" type of interrupts:

My current MSI mode utility configuration
After a restart to apply this change, I did a new the Polling Rate test with the mouse configured in 8kHz, the results are perfect now:

Stable polling rate even with Teamspeak in background
and in the CSGO menu moving quickly the mouse, I have almost the max of FPS:

Stable FPS in the CSGO menu
In game I don't have extreme stuttering anymore and I have stable FPS including with Teamspeak in background.
I hope this workflow will help other players to fix their performance issues with this mouse.
Note: I have to configure the graphic card to use the MSI type of interrupts after every update of the NVIDIA drivers
Source: reddit.com