This doesn't help much, but the 18-35mm and 50mm were very fast and smooth with the 7D Mark II...I sold them by the time I was testing the 1DX Mark II, but I would guess the full-frame 50mm would work well with it too.
They both work in AF mode. They can be "loudish" when the motor steps the focus. Speed is average. Movie Servo AF is not supported—that is the AF speed setting.
You need to switch off peripheral illumination correction, or you get strange looking artefacts.
Talking about the 1DxmkII here. General auto focus works with Sigma (and Canon obviously).
But there is a servo function that allows you to control speed of AF, and that only works with compatible lenses. This won't work with Sigmas, and also not all Canons. But it isn't limited to STM lenses either (even if performance might be best here).
The AF will be 'continuous' with Sigmas though, so they work OK.