Hi Dan,
The vertical GPU mount is compatible with the Asus helios GX601 case.
But sorry I do not understand what mount setup you need for a 3-slot 4090 gaming trio.
But this vertical mount BP-VTS-PCIE4 is compatible with a 3-slot GPU card, and it only can use with one GPU card.
https://shop.bitspower.com/index.php?route=product/product&product_id=7952&search=4.0
