If I’m not super mistaken, VXGI2 is + only. ( ie nvidia 900+, though the… 780 ti? and another 7-series card are the exception. )
But VXGI 1 is works on both, and only relies on the proper DirectX support. Though it has optimizations specifically for nvidia in the settings. (Material settings, I think? It’s been a while.)
To echo what you’ve said though. I’ve seen VXAO only in Tomb Raider(2, atleast.), I think.
Never seen or heard of a full on VXGI implementation, and with the spectre of DXR/RTX looming overhead I suspect anyone interested in eating the performance cost will jump straight to DXR/RTX.