There's only one SFF Vega card, the Powercolor Vega 56 Nano. Vega cards have DisplayPort 1.4. They have a maximum output resolution of 4096x2160 over either DP or HDMI, though, so you'll need to combine two outputs to run the monitor at 8k. That's how the monitor is designed too - it requires dual inputs and display tiling to work. I have no idea if Vega cards are capable of resolutions beyond 4k with tiled displays, but that sounds likely (to the GPU, it's not one but two displays). With DP1.4, it should be possible to run this at 8k60, but don't quote me on that.