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In practice, although seldom in theory, most Christian denominations are 'mystery religions' with a two-level structure: an outer part for semi-adherents, and an inner part for a higher-level elite.
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In Eastern Orthodoxy, the monastic life is highest (and monks are not usually priests); in Roman Catholicism priests are an inner circle, higher than laity. This is obvious.
But even among Protestants, the church organization is often - in practice - two layer. In evangelical churches it seems there is usually a wide outer circle which engages with the unconverted, and contains the recent converts and semi-attached.
This layer is all that outsiders and those who attend only public services perceive; but there is an inner circle of those who have leadership positions, with preaching privileges including leading home groups. (The mystery element in this is prayer, of a qualitatively higher intensity and duration. )
Mormonism makes the distinction explicit - with a wide circle of Ward 'church'-attending Mormons, and an elite of Temple Mormons selected from among those active and obedient, and for whom the potential level of theosis (accesed via Temple 'ordinances') is higher.
(Much as in Eastern Orthodoxy the potential level of theosis is higher - i.e. Sainthood - for those monastics who engage in ascetic disciplines.)
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I suspect that all long-term successful religions require this basic structure of an outer and public aspect; and an inner, secret mystery life for the elite.
Christian churches often emphasize the opposite, the absolute 'equality' of all believers, but ultimate spiritual unity is compatible with many forms of proximate hierarchy and specialization in organization.
Sometimes the distinction is explicit and celebrated, sometimes it is implicit and denied - but I think it is always there.
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