Is the AD8476 good for driving only 16-bit ADCs or can it also drive other ADCs
such as 18 bits or 14 bits?
Yes the AD8476 can also drive other ADCs.
The AD8476 is designed to drive 16-bit ADCs up to 250ksps, but it is capable of
driving other ADCs. 18-bit performance can be achieved by limiting the noise
bandwidth. Faster 14-bit converters can be driven as long as the 6MHz bandwidth
is enough to settle between samples (see Q5 for more info). The AD8476
distortion should also be commensurate with the ADC.