Thanks for the input Draco1962; greatly appreciated.
I was thinking they may work at the same time as the Virtual Pinball is very GPU resource hungry, whilst the Arcade would be more CPU resource hungry.
I was thinking I could run the playfield, backglass and Arcade screen off the video card and run the DMD off the onboard video card.
Can you try to pinpoint where the above specs may become a shortfall? Maybe purchase only 1080p screens for the whole systems and ditch the 4K screens to lessen the burden on the GPU?
I can see this new hobby is going to be an expensive one; but well worth it.