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In MN 43 we read:

"For what one feels, that one perceives. What one perceives, that one cognizes. Therefore these qualities are conjoined, not disjoined, and it is not possible, having separated them one from another, to delineate the difference among them."

In MN 18 we read:

"Dependent on eye & forms, eye-consciousness arises. The meeting of the three is contact. With contact as a requisite condition, there is feeling. What one feels, one perceives (labels in the mind). What one perceives, one thinks about. What one thinks about, one objectifies (papañcizes)."

Viññāṇa and saññā are not the same, certainly, but the difference is not possible to delineate.

Rather, it seems papañca is worth understanding, it seems saṅkhāra is worth understanding (sabbe saṅkhāra duḥkha), because these phenomena are involved with how dukkha arises. But trying to tease perception and awareness apart seems akin to shoving a wedge where one is neither possible nor needed. The very effort to do so appears to be papañca.