Follower overview: Lydia - Omni-guides/Tuxborn GitHub Wiki
Wait, we hear you thinking, isn't Lydia a vanilla follower? In fact, your first major vanilla follower?
Yes. Yes she is. We all know Lydia from vanilla Skyrim. But Tuxborn is running the Improved Follower Dialogue - Lydia mod, so for our purposes, she actually counts as a mod follower. This version of Lydia has much more in-depth characterization. She reacts to a lot more of Skyrim's main quest, and additionally to significant vanilla side quests as well.
This isn't different in Tuxborn--you still get her as a reward from Jarl Balgruuf when you're made thane of Whiterun. But the conversation you'll have with Lydia as a result is a lot different!
Modded Lydia doesn't have a built-in way to summon her. But if you track her with the UMF follower management mod, you can bring her back to you with UMF's Check command, should the two of you be separated.
While her mod changes her substantially, it does not change what kind of warrior Lydia is. She still functions best as a tank. Give her heavy armor, and either a two-handed weapon or a one-hander plus a shield, depending on what weapons you come across that seem best to give to her.
This version of Lydia will react to a lot of aspects about your character: your race, your skills, and more. Her MCM covers many of the topics she can comment on, and you can toggle off any you don't want her to talk about. You can also adjust how often she speaks, if you find you'd like her to be more or less talkative.
Note that her commentary on your various skills will also change as you progress in them.
Lydia is scripted to deliver significant character arc commentary in response to your reaching important milestones in the main Skyrim quest. In most cases, she'll automatically trigger these responses. But if she doesn't, try to talk to her and take any unusual dialogue options you see. This will keep her commentary triggering at the appropriate points.
She will comment on a wide variety of side quest content in Skyrim, and her responses may well be different depending on how you play them. Examples of this are In My Time of Need, and The Forsworn Conspiracy/No One Escapes Cidhna Mine.
By default, Lydia will react very badly if you join either the Thieves Guild or the Dark Brotherhood. This is by design of the mod creator, as the mod's intent is for her to support "good guy" playthroughs. This option, however, can be toggled off in her MCM.
Likewise, Lydia will react very strongly if she thinks you've taken to worshipping Daedra, and if you get her angry enough, she may outright attack you. So plan your use of her as a follower accordingly, especially if you have designs on acquiring the Mace of Molag Bal.
Last but not least, she will also react to events in both Legacy of the Dragonborn and Wyrmstooth.
This Lydia is custom voiced. However, Tuxborn's load order also includes two patches to give her interactions with Lucien and Inigo. It's important to note that these patches assume Lydia has her original voice! So if you're running Lucien, Inigo, or both, you may hear Lydia deliver lines that sound like her original voice actress. This is not a matter of her mod being broken, it's simply a matter of the patches not accounting for Lydia not having her original voice.
Lydia has a personal side quest, as well as an option to romance her. This romance is well set up, even accounting for the power dynamic of the Dragonborn becoming romantically involved with their own housecarl.
If you have a history of ignoring Lydia in vanilla and getting rid of her by letting her be Steward at a Hearthfire house, be aware this will not work with this version of Lydia. She is set up to specifically not be available as a Steward. You'll even have a dialogue prompt with her where you can ask her about this, and she will turn you down if you offer her the position, on the grounds that it will interfere with her primary job of defending you. This is very much by design on the part of the mod creator.
If your personal preferences lean towards not starting the main quest immediately, or if you dismiss Lydia and then re-recruit her later, be advised that this may make interacting with her a little weird. You may need to work through a backlog of her scripted responses before she catches up to where you actually are in your game.