I have a question about a build guide I'm following.

I'm a new player on PS4, and I've been following the build guide below. I have a couple of questions about it if anybody can help.

https://www.youtube.com/watch?v=YsiT8vsxeU0

1. Why does he have ice shot with 5 support gems in two different pieces of gear? My understanding is that essentially gives you two different versions of ice shot. Is maybe one of them more for single target damage?
2. When you watch the gameplay section, there's a very specific effect that happens around the enemies. It almost looks like there's a whirlwind of ice around them or something. I've tried all the gem supports, but I don't have the same effect. I'm wondering if it comes from a piece of gear that I don't have or if I'm missing something.

Any help is greatly appreciated. This game is super fun, but jumping into it is overwhelming since it doesn't explain everything, ha.