In my case its moment I see a triple, I instantly know it's a triple and well... 3 alternate taps and I'm done.
You can see is it a triple or double or stream/whatever based on how many circles you just... see there. I guess how well you do them is somewhat based on how well you can react. It can be hard based on the bpm+AR combo but the more you play different types of maps, the more you'll know about getting used to those.