To put it simply, for AC coupling capacitor to remove DC bias, it needs to first charge to that bias voltage. And to charge it needs to have a path for that. Op amp input is very high DC resistance and it may take forever. So you need to have some resistance after capacitor which creates a path for fast charging to this DC bias voltage and settle. Notice, that it is now a high pass filter. So you need to calculate your components for required low frequency cut off.
High pass filtering is another perspective how you can look at AC coupling. Notice, that if you have infinite resistance after capacitor, this filter will pass 0 Hz (DC), because it has infinite low cut off (no cut off at all) frequency. To block DC you must create high pass filter, there is no other way here. So you choose some frequency, lets say 100Hz, as a cut off frequency. Now all lower frequencies, including DC (0 Hz) will be attenuated (and for DC it will be infinite attenuation, it means complete blocking) and this is exactly whats is AC coupling.