I ran into the same problem
in my case modern standby wouldn't work usually if I had a USB mouse connected.
attempting the fixes to go to S3 sleep resulted in the machine hard crashing on wakeup
I ended up switching to a bluetooth logitech mouse to get around it the above issue with the USB mouse
In the case of hibernation this can be bad for you're SSD since it's writing Gb's of data to the disk from memory each time.
It seems to stay "asleep" (S0 modern standby) if it gets to the point where it does sleep (light fading on and off)
But sometimes I have to reboot it or try sleep a couple of times to get it to actually go to sleep which sort of defeats the point.
I think because it's software based in some cases some form of background app can prevent it from sleeping.
I suspect it would be a lot better if it went into the same mode of "sleep" that it goes into when there's no power cable connected
Since I think that's some lower form of sleep for modern standby. But I've no idea if there's even a registry fix for it.
Personally I would never trust a laptop in "modern standby" in a laptop bag without shutting it down.
https://rog.asus.com/forum/showthread.php?126967-Laptop-GX703HS-KF075T-Sleep-Mode-Issueshttps://rog.asus.com/forum/showthread.php?128570-Please-re-add-support-for-proper-Hardware-Sleep-S3-...
