It's expected that once you passed through a video card, you will be viewing that output on a monitor connected to that card, and using the VM exactly the same as any other computer. If you wish to remote in, you will need to implement remote control software hosted in the VM, exactly like you would if you want to remote in to any other computer.
If this thread were about a windows based system, RDP, teamviewer, nomachine, gotomypc, or any of that type of program would be my recommendation. Since it's mac, I'm not familiar with the best remote control options, but I'm sure they've been mentioned in the course of this thread.
tldr: Any remote access software that works with mac.