Did you read the article on it?
The first Season/Battlepass will not launch until after game release.
All that happens is the people who spend money get to sit in queues and be guinea pigs for the launch week hiccups.
Paragon points are capped, we can’t buy xp boosts, gear, etc. We can only get cosmetics and I think the accelerated gives you a few of the season milestones early. But not power.
There will be a single track of rewards with Free Tiers that are unlocked just by playing the game and leveling, and Premium Tiers which provide no in-game power or advantage over other players. The Free Tiers of the pass will provide gameplay boosts to all players—things which make the journey of leveling up a fresh seasonal character faster and more streamlined. In contrast, the Premium Tier rewards are focused on aesthetics, providing a huge value in the form of cosmetics and Premium Currency. Many of the rewards embody the seasonal theme, helping players show off their participation in that Season.