My general advice for simple and effective rinse+repeat falcon play
-Against bad DI, you can combo both of them well from zero out of Fthrow with a running C-hop F-air to U-air up-B or whatever.
-Against good DI ness, follow the Fthrow with an Upsmash to Uairs instead
-Against good DI pika, try Uairs or something IDK I just do whatever
If, for some strange reason, you end up having to hit them with something other than a grab from zero-
Upsmash works pretty well against Ness's dair, but his little *****-hands can't be beaten on that Utilt- don't approach from above
at mid percents, pivot horizontal Uairs against pika is good if you can learn to do those consistently (otherwise just do Uair and follow it with an up-B if you can, or a Dair for the kill if you're kinda near the edge, honestly pika's not gonna be at mid percents often if you're playing the BATTLECOW way)
Good Ness's get surprised by weird Fairs used at random times. if you hit with one of the kicks, he's meat.
Edgeguarding pika is kinda easier than people think, just look into the mind of your opponent to find where he's gonna up-B and then spike him out of it. Ness is pretty easy to edgeguard, just don't let him have the ledge.
Bairs are like OK to space with but mostly just run around when they're at 0 and then grab them and then they're dead.
What console tournies are you going to, may I ask?