Everything is done with command blocks. All that is left to Vanilla behavior is the mob following you. As for the attack, that is exactly how Zephyrs attack in the Aether II. You may be thinking about their old attacks with snowballs.
The Zephyr mob is made with a whopping total of 4 item models on a skeleton's head. The whole map is in vanilla, and will use command blocks and a resource pack heavily to make it feel as close to the real mod as possible.
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