How does Assassinate, Sneak Attack and Arcane Archer’s Seeking/Piercing Shot play together?

@JeremyECrawford How does Assassinate, Sneak Attack, and Arcane Archer's Seeking/Piercing Shot play together if it's the first attack of a combat?

And how does Sharpshooter play with Seeking/Piercing Shot?

— JHancho (@JHancho) December 19, 2017

If a feature, such as Sneak Attack and Assassinate, does something special when an attack hits, that special effect doesn't occur if there's no attack roll that hits. #DnD https://t.co/kvXPZ6B4li

— Jeremy Crawford (@JeremyECrawford) December 19, 2017