Two questions regarding new Eternals feature

Hi, I am debating buying the series 1 pass for unique eternals, but I have a couple questions;

First of all, if a player owns all the eternals, what use is there for the Eternal Capsules? Are they only orange essence at that point or can they be saved/rerolled for new eternals in the future?

Secondly, does buying singular eternals lower the cost of the series pass bundles in any shape or form?

Thank you!