Hopefully you are still on Windows 11, in the advanced display menu you can see what monitor is connected to which GPU.
Make sure they are all to the nvidia GPU.
Another test just in case, go to the device manager and disable the Intel display adapter GPU, whilst the BIOS is still set to dGPU it's still active and can be used by the monitors.
What was said in the other post still applies and its more of an issue with Windows when it detects hardware / monitors, it has the ability to re-sync the displays so all are impacted especially when you are on multiple / shared desktops as the GPU is scaling across.
But your setup is not easy on the GPU detection, the use of VGA to HDMI is a point of failure as this contains a DAC (physical chip to convert) which means the GPU does not actually detect and talk directly to the monitor, instead it's relying on the DAC for signalling so if this is now failing it can cause problems. Windows is also terrible on managing multiple displays and with laptops that are dual GPUs it's worse including the use of a displayport adaptor to HDMI is another source of communication mismatch to some displays.
But to keep things easier stick with the home setup as that is just DP and HDMI so should be minimal signalling issues. You say it sometimes happens whilst playing games? When exactly, upon starting the game or mid way through like you are actually in a game killing zombies and the screens flicker / reset?
