How to approach polytheism?

Is it possible to think that all gods and goddesses across all religions; beings we refer to as 'deities' actually exist? Or are they merely different manifestations of a single essence? Does each possess its own independent individuality, or is what we call 'multiplicity' simply a reflection of 'unity'?

In this context, another question arises: How should we approach the gods? Do all the deities known throughout various cultures coexist simultaneously? Or are they different reflections of a single being that appear in various forms according to each culture? Alternatively, should all these gods be understood as entities shaped according to the needs of humankind?