Gods do not float free in the Multirealms. They are fixed. Not in the sense of being incapable of extending influence - gods reach across enormous distances constantly. Fixed in the sense that their domain occupies a specific position in the infinite oblong, defined by the nature of their accumulated worshippers and the cosmic weight of their portfolio. Material worlds form in positions that reflect their mythological character. A world built on Norse mythology is near the Norse pantheon's domains. A world built on Egyptian mythology is near the Egyptian domains. This is not by design but by resonance - the worlds and gods reinforce each other across the Ethereal membrane in a feedback loop that spans generations.
A god's position in the cosmological structure is not political. It is gravitational. It is the physical consequence of what they are.
Proximity as Influence
The closer a Material world is to a divine domain, the more naturally that domain's deity tends toward involvement in the world's affairs. A world in the cosmological neighborhood of Zeus's domain will have more frequent storms of divine significance, will produce more clerics whose instinct runs toward sky-sovereignty and justice, will find that myths of sky-gods arise naturally in its cultures even without specific worship of Zeus.
All Mythologies Are True
Every deity that has ever been worshipped in any mythology, any ancient tradition, any game system, any legend - exists somewhere in the Countless Realms. Thor and Zeus can both be real. Anubis and Hades can both hold domain over aspects of death. Your cleric can serve a god borrowed from Greek myth while the party's other cleric serves an entirely invented deity. They are simply praying in different directions through the Ethereal.
Inter-Divine Conflict
Gods generally do not wander far from their domains. But a god who actively moves their projected attention toward another deity's home territory is encroaching. The history of divine conflict in mortal mythology is largely a reflection of these cosmological encroachments playing out through the medium of mortal events. When Mars decides to extend influence over a territory adjacent to Zeus's domain, Zeus notices. When Jupiter simultaneously backs Mars in that bid, the cosmological event creates ripple effects felt in the Material worlds of both neighborhoods.