Exoworlds are temporary worlds that will join and leave the universe. They can be any level. (If they were only Level 7+, then many players wouldn’t be able to experience them.)
Level 7+ worlds (often called Special worlds) will require atmosphere protection. This is a gating system to make sure that you’re ready for the world.
Level 7+ worlds will have their own resource profiles. They do contains the special material blocks: rift, blink, etc.
Atlases do work on the Exoworlds. But when the exoworld leaves the universe then the atlas will reset. (This is mainly for technical reasons and trying to keep things simple for us.)