@StephenCook The X-Controller will support VFD based water cooled spindles. It has 0-10V and 5VPWM, which should cover most.
Some of the low cost Chinese VFDs are very noisy and can cause issues. When attached USB devices you need to be careful about routing wires.
Some Advice: Use as short as USB cable as possible and keep the power cord to the VFD away from other wiring.