So, what is the big picture strategy going into facing ICs?
To me, I think its pretty apparent that if you can KO Nana, you should win the stock. However, I see hardly any discussion at all on keeping the two separated which I think should be the whole goal of the match-up. Learn the Nana AI so that you can abuse their separation to the maximum.
http://www.smashboards.com/threads/knowing-your-nana.307567/
I think its worth it to use this as a starting point to learn how the AI works. Oddly enough, playing against CPU is actually really helpful for learning a match-up. Play against the lv9 CPU and learn to abuse the AI on Nana. For example, if separated, Nana will take the shortest route to get back to Popo ignoring the danger in the way. So, you can charge an Fsmash at Popo, and then Nana will run right through your charging Fsmash. If the ICs ever have to recover with UpB, grab the ledge if the distance is right since while Popo gets on for free, you often get a free stock on Nana. Killing Nana is like getting the kill on Popo.
The AI on the ground is fairly obvious. However, the AI in the air I have not been able to figure out all that much, I think more attention needs to be paid to how Nana operates in the air above platforms, near the stage surface, and offstage both far and near. It always seems like Nana will prefer to fire one ice block when recovering from super high-far offstage. That would seem like very valuable time to get a Dair Spike on Nana at that point.
Match-up Staging
1) Work to separate.
2) Once separated, KO Nana.
3) Then KO popo.
And as mentioned before, Grab is wonderful at separating. Fthrow/Bthrow over Dthrow are more preferred since fthrow/bthrow have active hitboxes on top of falco, then have the active hitbox on the thrown IC for dead weight. The range of hitbox from fthrow/bthrow is larger than Dthrow. Even if you miss, the moves are much faster. I think never use Dthrow as it does not knock the other one away from you. Only disrupts them slightly.