Can't wait for this case! It was very clear that SFF cases are not there yet for a RTX3090 Founders Edition, so I moved that build to ATX. The 3090, especially the Founders Edition is just one massive heatsink, and it relies on case airflow to cool itself. The fans do their work to keep the die cool, but by doing so heat up everything in close range of it. With sandwich SFF cases, that's the underside of the mITX board, which houses the CPU, PCH, SSD, VRM, ... all in a couple centimeters squared.
So, this ATX build is only temporary, because the 3090 is too good to leave unused until a cool case like the C4-SFX arrives. Currently using a H510 loaded to the brim with Noctua 3000RPM industrial fans, it's loud, it's obnoxious, it's present, it's ... ATX.
So, I can't wait for this 12th gen to arrive, and then build the 3090 in this C4-SFX! Yeah!