I think some of the intermingling of different English terms and conflating their meanings with regard to what Shankara and Advaita says leads to some of the misunderstanding. I do not understand what is meant by the word 'level' or 'levels' in the concept of Vedanta. Use of the words reality and existence have better meanings as to the Sanskrit and what is meant by Shankara and Advaita. In one of the other similar questions on this topic referenced in the comments above, The Vedanta Paribhasa of Dharmaraja Adhvarindra is referenced as a source (see here, pp 84-85 - http://estudantedavedanta.net/Vedanta%20Paribhasa%20of%20Dharmaraja%20Adhvarindra%20-%20Swami%20Madhavananda%20[Sanskrit-English].pdf). The verse says:
EXISTENCE IS THREEFOLD -
Or (we may say) there are three kinds of existence: absolute (Which remains uncontradicted for all time.), conventional (Which abides till the realisation of one’s identity with Brahman—that is, what is popularly known as real.) and illusory (Which is destroyed as soon as the obstacles to proper vision, such as distance, diseases of the eye and sleep, are removed ; e.g. a mirage.) Absolute existence belongs to Brahman, conventional existence to the ether etc. [the sensual universe], and illusory existence to silver in a nacre. Thus the perception, “The jar is existent,” is valid, as it treats of conventional existence. In this alternative, the negation of a jar etc. in Brahman is not a negation of those things as they actually are (That is, as phenomenal entities.), but only as absolute reality (Which Brahman alone is.). Again, in this alternative, we should understand that in the definition (Given on p. 81, ll. 10-13.) of unreality the absolute non-existence is to be so qualified as to convey the additional idea, “And the counterpositiveness relating to which is characterised by absoluteness.”’” (The above words should be added at the end of the sentence setting forth the definition.). Therefore the inference about the unreality (of the universe) is valid.
To summarize this verse, Brahman is the One Absolute Existence, the sensual universe perceived has a certain objective reality. As Chandradhar Sharma writes in his A Critical Survey of Indian Philosophy pp 271-2 (available here - https://archive.org/details/IndianPhilosophyACriticalSurvey):
...do not deny the objectivity of the external world, as the objects appear as objects to the knowing subject, and secondly, because they hold pure Consciousness which is the same as the self-luminous Self to be the permanent background of all phenomena...When it is maintained that pure and permanent Consciousness, which is self-luminous and which transcends the subject-object duality, is the only reality and the world is only its appearance, the criticism of Shankara falls off the mark because he himself believes in this view...Shankara...is keen--and herein his greatness lies--to emphasize the phenomenal reality of the world. Secondly he wants to prove the unreality of the external world not be saying that it does not fall outside consciousness but by saying it is essentially false (mithya) because it can be described neither as existent nor as non-existent (sadasadanirvachaniya).
Another way to think of this is rather than 'levels' think of the concept as three states of consciousness as described in the Mandukya Upanishad. In the dream state dream objects are perceived which disappear once we wake up. In the waking state we pereive gross objects. In both these states, objects are pereived. In the dreamless state, no objects are perceived, there is no knowledge of multiplicity. And the underlying state of all three states is the Turiya.
Brahman is the One Absolute Reality; the conventional, perceived universe has a certain relative reality; and mirages have a certain illusory existence. When our sensual perception changes, the mirage disappears and we see the sensual universe. When the veil of Maya is removed, this sensual universe disappears, Brahman Alone Abides. Three 'states of existence' so to speak, but only One Real Existence that underlies all the 'existences'.