If SYNC pin is high Is the SDO pin of the AD5722R tri stated ?
Can several AD5722R devices share one common SDO line on the data bus and just be selected by the SYNC input?
Or will each of them need its own SDO line or be daisy chained?
The SDO is enabled by default. The SDO lines power-up to the same level so you could connect them together and after power-up disable each of them one-by-one. This can be done via the SDO disable bit in the control register.
If the SDO output is disabled via the SDO disable bit in the control register, it is automatically enabled for the duration of the read operation, after which it is disabled again.