You know how most characters have recoveries that come from beneath the stage?

If you get someone off edge, pull a bomb jump out and throw the bomb directly down.

From here you have two options:

1. Detonate before it reaches an opponent. This is risky, because if you detonate too early, you won't hit them, and they'll recover with an advantage since you're still off edge. However, it's also high reward, because it will almost certainly kill at all percents.
2. Wait till the bomb hits them, in hopes it gimps them, and then detonate immediately. This option is low risk, low reward. Some characters once gimped can just begin their up special once again before detonation, allowing them to recover. Some characters have up specials that clank or have super armor or are straight up resistant to the bomb and will go thru it back to ledge.

I think the best thing to do is to mix it up, so that your opponent is more prone to up special recovery earlier than usual and then you instead of going back to stage you can down air or neutral air when they recover right at you.

I prefer to detonate earlier than usual for 2 reasons:

1. I don't like the idea that they could potentially catch the bomb and hold it.
2. I don't like letting the opponent dictate when I detonate (i.e. waiting for it to hit them).
3. The bomb will always have upward knockback, but where you're located depends on which trajectory (i.e. the further toward the blast zone you are, the more the blast zone will be a danger, but if they're on the stage side of the bomb, the bomb will actually detonate them toward the stage. So I prefer to not let them get on the stage side of the bomb, thus I detonate early.