The turn-based mod for Pathfinder: Kingmaker was such a great addition that developers Owlcat included a version of it with the free Enhanced Edition upgrade, as well as an option to wear ugly clothing for the buffs without it showing up on your character (like that hideous expert's hat), which was also inspired by a mod. Even with a couple of the best Pathfinder: Kingmaker mods being incorporated into the base game, there are still plenty more worth trying.
Kingmaker adapts the complicated tabletop RPG system of Pathfinder, which is full of 'noob traps' that punish experimentation, so new players will benefit from tweaks that make it more forgiving, while experienced players can dive into mods that add even more of the tabletop system's options. And everyone can benefit from the ability to rotate the camera.
The next in the series, Pathfinder: Wrath of the Righteous, is currently in beta and already has a healthy mod scene of its own thanks to Kingmaker modders who have started converting their best work to be compatible with the follow-up. If you're looking at the original, however, whether you're returning to unlock that secret ending or playing for the first time, these are the best Pathfinder: Kingmaker mods.
Unity Mod Manager
The Pathfinder games are made with the Unity engine, so you'll need Unity Mod Manager to get them working. If you're already using software like Vortex to handle your mod loadouts in various games you can still use that to install Pathfinder mods, but you'll need to bring up Unity Mod Manager's UI in-game to enable them and alter their settings. Press Control + F10 to open the menu while you're playing.
Bag of Tricks - Cheats and Tools
Bag of Tricks lets you toggle over 200 game-changing options. I've been using it for dozens of hours and am still finding new things. While it includes straight-up cheats for editing stats, money, and XP as well as killing or resurrecting NPCs and so on, it's useful even if you're not a dirty cheat. Bag of Tricks adds features like camera rotation (defaulting to the , and . keys), a UI toggle (press ; for that), alterable zoom distance, and the ability to control summoned allies rather than leaving them to the AI. You can access your pets' inventories, instantly complete kingdom events, check your romance progress, and more. Something for everyone.
Pathfinder Iconic Portraits Pack
Kingmaker's portraits are great, it's just a shame there aren't more of them. If the basic selection doesn't cover the exact character you want to make there are plenty of portrait packs to download, but they sure do lean toward chesty ladies and dudes with Viking haircuts yoinked from DeviantArt. The Pathfinder Iconic Portraits Pack is a better option, since it draws from the tabletop game's iconic characters, meaning its portraits won't clash with your other companions. They've been edited to have appropriate backgrounds too. But if you'd rather have Icewind Dale portraits or Geralt and Yennefer from the Netflix Witcher show, I won't stop you.
Craft Magic Items
Being able to make your own potions, wands, scrolls and other magic items can be a boon for certain builds in pen-and-paper Pathfinder, making wizards less reliant on constantly napping to get their favorite spells back. That's even more true in Kingmaker, which bumps up the number of encounters you face each day so much it encourages sleep-scumming your way to victory. This mod adds all the item creation feats from the tabletop rules: Brew Potion, Craft Arms and Armor, Craft Wand, Craft Wondrous Item, Forge Ring, and Scribe Scroll. Once you've learned one of those feats, you'll need to bring up the mod manager window to get crafting.
Call of the Wild
Another mod for adding tabletop rules, Call of the Wild throws in a heap of additional classes. It adds the Antipaladin, Arcanist, Bloodrager, Brawler, Dawnflower Anchorite, Hinterlander, Holy Vindicator, Hunter, Investigator, Occultist, Oracle, Psychic, Shaman, Skald, Spiritualist, Summoner, Warpriest, and Witch, as well as feats, spells, and class abilities for them and the vanilla game's classes. On top of all that it adds more subclasses, of which my favorite has to be the variety of fallen paladin called the 'Vindictive Bastard'.
If that slow zoom toward the book that serves as Kingmaker's opening menu drives you nuts, here's a mod to get you past the animation and right to the options with no messing about.
Highlight Learnable Scrolls
While one use for scrolls in Pathfinder is the old fire-and-forget, some spellcasters can also learn spells from them to permanently add to their repertoire. A real 'does what it says on the tin' mod, Highlight Learnable Scrolls makes scrolls glow green in your inventory or the shop if your selected spellcaster can learn them. There's an option to change the color for colorblind players or anyone who just really hates green.
The best Pathfinder: Wrath of the Righteous mods
There are definitely some Wrath of the Righteous mods worth checking out too. Inspired by Kingmaker's excellent Bag of Tricks mod, Toy Box lets you edit your stats, change your quest progress (helpful if you hit one that's bugged), disable fog of war, teleport around the global map, ignore class and feat restrictions, and more. You can even pick a different mythic class each time you level up, starting at level one. Meanwhile, Avalonica's Portrait Packs have "personally hand-googled" faces for Wrath of the Righteous characters including kitsune and tiefling characters.