1. Mass Production
Mass produced armor is relatively uncommon. While it is certainly within the realm of the Cosmic Era's ability to mass produce power armor, to equip legions of power armor troopers. There are several limitations against this. Most of the CE powers are decentralized and the tempo of was is geared towards small skirmishes, and no all out wars. Within the various member states there are regular production runs, but these are not for stocking regiments and battalions. These production runs are for specific megacorps, nations, and so forth. The suits are custom kitted and made for each customer.
These are readily available, either through salvage, the black market, international weapons markets, and through security contractors provided they have the right licenses to own and operate them. These are 'generic suits' of armor.
2. Custom Made
The polyforge and pocket factories allow for small groups with sufficient funding to secure special and custom made power armor relatively easily. While this does require money and suitable legal permissions (licensed security contractor for example). These custom made units allow for private organizations to stock their own security forces, and for special environment locations to have their own armors custom made for their specific needs. A large manufacturer isn't going to spare production time for a seacology that needs just a dozen or two light 'squidsuit' power armors, where a smaller pocket factory would be happy to fill their order, and to add the resulting suit to their catalog of offered goods.
3. Standard Template Construction
The majority of suit customization is cosmetic. There are only a handful of chassis designs, and most of designing a suit is based around picking a chassis, adding whatever equipment is needed for the task (aquatic,radiation filters, etc) wrapping it in a carapace, and then adding accessories. Computers handle most of the work, and the polyforges and assemblers do the rest. The vast majority of suits share a large number of parts making them easy to repair, and many are interchangeable with a modest amount of effort. Designing a new suit can be done in a hours to days, and not years, or even decades. On the other hand, core components like basic chasses and such can take years to design, and these are generally the products of larger corps, and they get a licensing fee for suits build with their IP.
4. One of a Kind
One of a Kind suits are uncommon, not not rare. Any polyforge that can handle metal can make power armor components. That means that the largest impediment to making a one of a kind suit is jailbreaking the forge so that it can be used to make the pieces of weapons and armor to make the chassis and other components. Blueprints and patterns can be found easily on CogNet black feeds, and through the Silk Road. This allows for a dedicated cell or individual to make one of kind suits of armor. Unlike pocket factories, this process can takes weeks or even months, depending on the size of the forges being used. This is how terrorists, villains, and such can equip themselves with a wide variety of armor suits without having a large infrastructure to draw on.
While occasionally mentioned, hardsuits haven't really been addressed. A hardsuit is a civilian power chassis, frequently unarmored, or minimally protected. These suits are not used for combat purposes, but it isn't hard to convert a construction hardsuit into a makeshift power armor suit, much like turning a bulldozer into an armored vehicle only takes a welding rig and determination. Civilian hardsuits overlap with industrial mecha. These suits follow most of the same rules as power armor, but someone willing to hack a polyforge is more likely to make a Westek T-51b power armor suit than a Caterpillar P5000 power loader.
The use of arcanotech and power armor is fairly common, but the prevalence of parapsychics willing to button up into a suit of armor is far shorter than the supply of suits. The remedy to this is elixer and synthetic parapsychics, aka parasites. These bottle born troopers can use and control psychoframe armors, and not so unique and powerful to reject being controlled by the people who made the armor and employ them. This allows for power armors to be made that are otherwise in defiance of the laws of physics. The ubiquitous lightning armor (Shocker, Electro, Static Shock) can be aimed and controlled by someone who has electrokinesis, while a normal person trying to use it is going to be a walking Vandergraff generator with no ability to direct or control their discharge potential.
Power Armor can be broken down into five size categories.
1. Exoframe - an open architecture frame that adds strength, potential hardpoints, special equipment, but no armor.
The APU suits from The Matrix trilogy are large exoframes, heavily armed, but leaving the pilot 50% exposed to literally anything. The combat suits from Edge of Tomorrow also fit, adding strength and gun mounts, but leaving the pilot like 75% exposed.
2. Ironman - a light carapace type suit, unlike the namesake, these are too light and too form fitting for any internal weaponry, and require external weapon systems, and might even mount an armored backpack for power supply purposes.
Ironman and War Machine are the best examples, Ironman is sleek, War Machine is all about the bolt on gats.
3. Standard - a bulky mix of armor, firepower, and utility.
The Ironmonger, Terran Space Marines from Starcraft.
4. Heavy - the standard suit on steroids, with bulky armor for stopping heavy and anti-armor weaponry. Slower, but more firepower
The Imperial Space Marines ala Warhammer 40k, the Hammer drones from Ironman 2
5. Avatar - the largest power armors blur the line between superheavy infantry and ultra-light mecha. These are relatively rare, as mecha weapons and anti-armor weapons are effective against them, though infantry weapons are dramatically weaker.
The Hulkerbuster suit, or the AMP suits from Avatar, anything large enough for the pilot to sit completely enclosed in the torso, without their arms and legs actually in the extremities of the suit.