Answer:
For isolated high performance ADCs, keep one eye on isolated clocks and a second on isolated power.
SAR ADCs have traditionally been used for lower sample rates and lower resolution. Nowadays, fast, high precision, 20-bit SAR ADCs sampling at 1 MSPS like the LTC2378-20 and oversampled SAR ADCs with 32-bit resolution like the LTC2500-32 are available. When designing for high performance to utilize the ADC performance, very low noise is required across the complete signal chain. When additional isolation is required for a signal chain, performance will be impacted.
There are three isolation topics to consider:
Isolated power to ensure the hot side is powered