I thought it's fairly difficult to punish Pit while he's recovering. UpB has invincibility frames during his ascent, and SideB has super armor. I can punish UpB with Dsmash only if he's hugging the stage walls, and I normally would catch SideB recovery with Dtilt and the 2-frame vulnerability that puts him into a kind of a 50-50 situation with Dair/Uair.
Maybe I explain myself in a bad way, surely because of my lack of knowledge in english language.
It doesn't matter if Pit has invincibility frames during his ascent on UpB, there is NO risk on trying to gimp him. So is a win - win situation.
According to the Side B issue, it's a visual verification and decision. Pit will never (at least in my opinion) recover with Up B when he can do it with Side B. So it's pretty easily to detect which way he will recover and react according to that.
Also when I said edge guard; is about putting pressure and do your enemy make a mistake, it's like when Sheik waits for you on the edge with a shield. She's not doing anything at all, but she cover almost every option and it's doing pressure and limiting your chances.
By edge guard you can position yourself in a distance where our Fsmash reach the opponent but his get up attack can't touch us. You can do exactly what Sheik does, just get at the edge and shield for the invincibility frames to end. After that you punish with a Dsmash or short hop dair.
By the way, I forgot: I would not recommend to intercept the Side B, just wait or shield if your shield isn't low.
I hope this could have been clarifying, sorry for my mistakes in english.