There are multiple pantheons. Some members are in multiple.Do you pick a single pantheon?
Depends on which setting.Do you pick a pantheon for each kind of people (elves, humans, dwarves)? Do you pick pantheons for regions? Do you use real-world pantheons, D&D setting ones, or totally homebrewed ones?
I usually do actual homebrew religions so gods are in pantheons based on the religion.
In my Classic setting, gods are in "racial families". There is a Human Pantheon, Dwarven Pantheon, Elven Pantheon, Dragon Pantheon, etc. Some are D&D members. Some are real world members. Pelor and Zeus are brothers as sky gods and members of the Human Faith. Their sister is Canada, human goddess of winter.
But in my Klassic setting, the Sky, Earth, Sea, Space, Cities, and Underworld have their own pantheons. Each with their own gods. They are all general personifications like Mother Earth or Father Time
In the K setting, every major faction is blessed and you get free spells casted on you in emergencies if you help a faction beloved by a god.Does this only matter if there are cleric PCs?