You edge guard ness NOT by jumping into pkt1. That is a very rare opportunity that you can take somtimes if your feeling brazen. But really, if you choose to "go for it" then you cant stall or decide. You just have to act.
Typically, you edgeguard ness by forcing him to recover low. EVERYONE almost i would argue has the chance to do this, seeing as Ness both telegraphs where he's recovering, and that the last half of his PKT2 hitbox doesn't have the greatest priority. My recommendation is either
1. use edge invincibility frames to hit a ness
Or
2. Use an attack from the ground to punish where you think he's going to "slide across" or end up above. Smash attacks are always good, or retreating bairs.
OR
3. Bair/fair him with one of your characters, with the largest hitbox you got. Typically, you want to aim to hit him in the second half of pkt 2, so usually you actually want to stay on the ground, but mobile enough to get to wherever you think he's going to go
Once he's off the stage and below, he will try and recover low and will likely be unable to sweetspot the edge. At that point, you get a lot more options.