difference is while luffy got his high poison resistence from being poisoned near to death and recovering, choi got his from eating poison fish and swimming in poisoned water for centuries. and he wasn't really trying to be immune to poison. there just wasn't anything else for him to eat.
and he doesn't get power of existence until a few thousand years after he ended up in the abyss. he just thought he was training under his goddess and each world was just set up for him to get stronger. he doesn't really unlock it until he throws down with a avatar for half a year.