@benzitor
OK, so i found that in plugging to the second HDMI, the pi4 that didn't work now work with this image.
But the Pi400 is still not. No idea why. Is there any ways i could make it work ? I actually built this on Pi400, then finalized on Pi4, but the 7.2.1 did not show any problems... i will try to remove the Overclocking ... in case.
Please update one more time soon to give love to Pi400 ( overclock, special options, etc ) as it is the best Pi4 but now it feels like a leftover ( like the Pi0 though )