Vulkan vs Multi-GPU - Anyone has experience?

The Vulkan specification (with extensions) does support multi-GPU and multiple video outputs. However, I’ve never seen any demo showing this feature (yet).

Can someone confirm whether that’s supported with an Nvidia Geforce and/or Quadro card?

To be precise, I’m looking at a game-like application that would use two graphics cards and two LCD monitors, one monitor connected to each card. The idea is to connect two HMDs to the same game, each HMD having its full dedicated GPU (both for rendering and video output). I would even be interested in scaling it up to 4 cards if possible.

Please note that I’m not interested in connecting two DisplayPort to the same GPU because that means the final frame buffer of the second card would have to be copied over PCI-Express to output on the first card. At 4K resolution, that’s a significant performance hit. So I would need each card to do their own video output over DisplayPort.

Anyone knows how well this is supported on Geforce and on Quadro?
Hands-on experience would be very interesting to hear.