Can all Destiny 2 users play together, regardless of edition?

Solution 1:

You can still play the game together. The Deluxe version include the following:

• Destiny 2 Base Game

• Destiny 2 Expansion Pass: Get access to both Expansion I and Expansion II, offering brand new story missions, cooperative activities, competitive multiplayer, and a wealth of new weapons, armor, and gear.

• Premium Digital Content:

  • Legendary Sword
  • Legendary Player Emote
  • Cabal Empire Themed Emblem

(Source)

The deluxe edition pre-purchases the first two expansions essentially. You can always buy those separately. If you don't purchase them, you won't be able to take part in any of the content that comes with those expansions. You won't have access to the "Premium Digital Content" either, but that shouldn't impact being able to play with one another.