RayGuns and Rocketships
Distribution and Dynamics of *Cultures
The number and disposition of *Cultures within a given Galactic Hex is primarily determined by the stellar density and the requirements of the Campaign. Specifically the Technological Level [T/L]. And the Temporal Milieu.

The Table below provides a list of Campaign Types and Ranges of Influence.
N.B. The two columns are not necessarily related especially once the Influence reaches Galactic proportions.

Level Card Campaign Type
Range
I The Magician New Frontiers discovering FtL technology, a culture discovers a bright shiny new Cosmos to play with. But have they been here before? Or is it some very humanoid alien species? Local Backyard
(Less than 21 lytes.)
II The High Priestess The Great Explosion (Culture in Flight) discovering FtL, a planetary culture splits into a multitude of memes. Each colony world becoming culturally unique. The problem: how to weld these disparate factions into a Federation. Local Neighbourhood
(Less than 210 lytes.)
III The Empress Star Rush there's a Fortune (or at least a Reputation) to be made out there. The Rugged Prospectors; Trader Teams; Intrepid Explorers; and other bloody minded individualists rough it out on the fringes of civilisation.
InterStellar
(Greater than 210 lytes.)
IV The Emperor Controlled Expansion FtL is tightly controlled by the Military, MegaCorps, Planetary Governments,...
Intra-Arm 1
~500 lytes
V The Heirophant Static Either the Homeworld has exhausted its pioneering spirit or the Over-Government, in order to consolidate its gains, has called for a respite.
Inter-Arm
~1000 lytes
VI The Lovers Second Diaspora After a Collapse the Culture re-emerges to rediscover Lost Territory. Not necessarily from the original Homeworld.
Galactic Sector
10,000 lytes
VII The Chariot Controlled Disengagement The Authorities are in the process of retreat, naturally masquerading as 'redeployment'. Either in the face of a powerful xeno-culture, homeworld unrest, colonial revolt, or just because the Universe is too Big! (Cosmic Catatonia.)
Colony worlds are being abandoned, left to their own reserves...
Intra-galactic
100,000 lytes
VIII Justice Post-Colonial pocket empires/federations compete to discover and influence other star-faring cultures. After the dust settles, the Stellar HyperPower is attacked by a race of vicious xenophobes! Galactic Backyard
(Satellite Clusters and Dwarf Galaxies)
IX The Hermit Imploding as VII above but no attempt to hide the Collapse
Galactic Neighbourhood (Local Group: GMC, LMC, Andromeda and others)
X Wheel of Fortune Ouroburos a diverse Star Culture expands bilaterally right round the Galactic Disk and discovers itself coming the other way. The question is... do we recognise each other?
Inter-Group2
XI Strength Galactic Hegemon a single stable HyperPower rules the Galaxy with a Neutronium Fist. (Presumably some sort of Precursor Artifact!)
Intra-Group
XII The Hanged Man The Galactic Milieu stable, static, stultifying, shallow, stagnant and other statistics beginning with 's'. Until a group of AAs come along to stir things up.
Intra-Association Galactic Groups are grouped into Associations.
XIII Death Cultures in Flight from a Galactic Catastrophe or a race of vicious xenophobes, a Great Diaspora reaches across a Greater Rift... to rediscover their origins! Inter-Association
XIV Temperance Galactic Con-Sapiency an even handed 'democracy' with elected officials behaving like autocrats. Naturally some Sapients will be more equal than others.
Intra-Cloud Associations into Clouds.
XV The Devil Galactic Con-Spiracy on the surface: just lots of Cultures "just getting along with each other"; in the depths: a subtle OverGovernment, pulling on the Super-Strings, manipulates the masses. Inter-Cloud
XVI The Tower Stellar Relocation from simple regularisation of stellar distances - Star Hubs: synthetic close packed clusters of stars and cultures. To stellar caravans: stable groups of stars setting out at sub-light speeds for galaxies anew.
Intra-Cluster Clouds into Clusters.
XVII The Star Galactic Reengineering a galactic sized Dyson Globe, a Galactic Disc and other such HyperScientific fancies. Intra-SuperCluster and so on
XVIII The Moon Meta-Temporal The barriers between temporal dimensions are broken. First to fall: access to the impossible realities. The meta-worlds of myth and fantasy.
XIX The Sun Para-Temporal Access to the parallel worlds of increasing improbability and decreasing divergence.
XX Judgement Ortho-Temporal 'Normal' time travel up and down "The Line" with all the causal ramifications on your campaign!
XXI The World IntraSystem here the inhabitants of a planet find an ancient (alien) starship or an enigmatic stargate lurking in a remote orbit. The culture bootstraps itself from a stone age, ...medieval, ...steampunk, ...contemporary, ...interplanetary society into an interstellar one. Discovering a vast array of mysteriously deserted but habitable worlds.
O The FOOL Out of the (game) system!

Notes:
1 The Voids between the Arms are still a barrier either for technological or psychological reasons!
2 A true Galactic Milieu, reaching out between the Galactic Void to the next nearest Group.
The Temporal, Para-Temporal and Meta-Temporal remain firmly out of scope for the typical Serfs' Up Campaign.
But a routine fact of life for weary Arcane Adventurers!