BluetoothRemoteGATTCharacteristic.startNotifications() does not capture indications.

'A' does make sense.
I just thought 'C' would be more flexible. So 'C' can be 'A', can be 'B', or even something in between. Like:

function myRespondASAPHandler(event){
  NRF.confirmIndication(event);
  //do something ...
}

function myRespondAfterDoneHandler(event){
  //do something
  NRF.confirmIndication(event);
}
...
 characteristic.on('characteristicvaluechanged', (event)=>myRespondAfterDoneHandler(event));

Response "After Done" will serve scenarios where processing of a message may take time. So it will prevent flooding the Client by too frequent indications. Otherwise some additional synchronization logic should be done, like skipping next coming indications if a current one is still in processing.