CptT95
The g9 neo has like 95% of the pixel count of 4k roughly
I see that a single connection has limitations as I already know due to bandwidth capacity, I don't see anything about max CARD output limitations IE
Combined bandwidth of all display outputs
One G9 at max res and hdr and refresh rate is within the limits of one DP 1.4a port+DSC with room to spare
One 1080p panel at 240hz is similar to one 4k panel at 60hz then 2x 1080p panels at 60hz is roughly equal to 4k at 30hz
So I have 4k 240hz plus 4k at 60hz plus 4k at 30hz for total bandwidth out of card
That's with dsc on the first and the rest is well within limits of dp 1.4a/hdmi2.0(2.1)
EDIT- btw I never knew there were still limitations when using all 4 ports on the gpu, specially with mix of 1080p with single high res display
The workstation/pro level GPUs have this sort of thing listed in their spec sheets. I'm not sure if this info is buried in a user manual for consumer GPUs though. Even the lowly T600 (cut down 1650) can run 4x 4K@120hz, so I'm surprised you're having issues like this.
The issue could also be with Windows Display Manager not liking displays with different refresh rates on the same GPU. It apparently works fine with divisible increments (60/120hz, etc.) or by splitting displays on different GPUs, but I have yet to verify this myself.