Planetary control is not measured by percentage of planetary occupation but by ownership of specific points on the planet. Administrative sectors are nearly universal and often the location that provides official changes of ownership on the strategic map. However, this leaves the way open for criminal elements to do their thing without overly bothering their host, as they will worm their way into urban centers and set up rural outposts to further their nefarious plans. Which is usually making handfuls of credits at the expense of the owner and citizenry.
Other times things can get more complicated, with a set of objectives that might have to be completed in a specific order to openly invade a world. A garrison inside a shield alongside the administrative center may need the shield taken down before combat units can effectively reduce the hostile presence.
Speaking of which, unit sizes. Ground forces will generally be used in Companies. This is not a Clone War of old, you don't have millions of expendable soldiers to toss at the enemy. Militia and other garrison forces will generally be strong in number but, as they cover the whole planet for a great deal of duties, are limited in their response and vulnerable to sabotage or subversion.
Military equipment, from blaster rifles and uniforms to small warships, are built at their respective Landmarks. These Factories (for ground forces) and Assembly- or Shipyards (for space capable assets such as fighters and corvettes) are tooled for a specific product and will build that from a base pool of build points that is divided by the cost of the unit to get the number produced. Operating these Landmarks will usually cost Affluence, also known as your liquid currency, to represent purchasing the materials or finished product with your limited budget. Units may also cost upkeep, though that is a bit too granular for me outside of notable things such as large prize vessels your limited emergency powers explicitly do not cover.
You know, I never did learn how Star Wars handles militias. Like everyone and their mother seems to have a space ship of some sort with guns not being particularly hard to obtain. Yet the Trade Federation with all of their money didn't even employ mercenaries beyond what personnel they got through Count Dooku and Grievous. They just basically printed robots.
Even the Rebellion formed from gathered assets of important people like Leia's father and their personal troops and made a fighting force out of it. They hired people discontented with the Empire by the bunch but at that point they were a political, economic and military entity all on their own. It, I don't know, puts to question the legality and traditional place that militias have?
Like, would people just considered them thugs until our influence was such that we could just cover them with a nice paint of legitimacy? Because there is no way to tell the difference between a group of armed locals and people who want to rob you? I assume that Jabba had actual law enforcement of sorts in Tatooine before the Empire made him pay lip service, if only to enforce the rules that he personally wanted enforced, but if they existed they clearly were thugs.