i can tell you about the nanao ms8 but not about custom res from pc's
ms8 are manually switchable 15khz and 24khz via a jumper header on the chassis itself,they can handle low resolution and medium resolution
I would imagine all you need to do is make a custom res on you graphic card properties to match either or both
ms8 are a robust chassis but i do not know how high the resolution can go before the horizontal output transistor blows,in other words unless your operating system starts and stays at 15khz or 24khz it may damage the chassis.
I believe the j-pac was designed to prevent this happening