You could certainly use S/PDIF (the one by the Wordclock connector).
A mixed setup is fine, but you should avoid having the sync signal pass through pieces of equipment – it is best if it fans out from a single point.
For a complex system W/C is often preferrred, because you can easily daisy-chain the sync connections (as long as you understand termination), and it may have lower jitter which can cause a slight but probably imperceptible distortion reduction.
