I feel like those Nairs in the beginning (vs bowser) looked mad slow compared to how it looks IRL. The application of repetitive FC nairs isn't that useful. Sure u can pillar the shield, but even when u hit them, they only take like 13%? Thats nothin compared to falco's pillar that starts combos. I rarely use repetitive nairs just cuz they dont lead to much.
If u scare them enough with ur pillar, u can often keep them in the shield and mix up a grab in there, id do that rather than just keep on nairing. The shield stun of a nair doesnt allow for u to combo into a grab, but the fear does. If they are good though, they will pick up on this, so u gotta mix it up. Buffer roll completely thwarts pillars of any kind, of course.