While Skyrim may have plenty of NPCs who will follow you around, carry your burdens, and even agree to marry you in spite of the fact you probably reek of dead mammoth, there's definitely a limit to how much personality they have. (Which is why some of the best Skyrim mods are the ones that add fully voiced followers.) Warden of the Coast (opens in new tab) is a newly released mod for Skyrim Special Edition that adds a new questline, locations, and nine "Bioware-style" companions.
Each of those companions has their own loyalty quest, and thanks to 27 hard-working voice actors, Warden of the Coast includes more than 9,000 lines of recorded dialogue. Three of your companions can accompany you at any time, Dragon Age-style, and will let you choose their perks, skills, and attribute increases as they level up. And yes, some of them can be romanced.
Warden of the Coast's storyline sends you to an island where Oblivion gates have opened. You'll have to do battle with dremora and prevent the daedric lord who is behind it all from achieving their schemes. The main quest involves choosing between factions, and you can consult your companions to see how they feel about each option. It includes a "dynamic companion regard system modified through dialogue, player kills, and quest choices."
Modder TheBawb says it should take 10 to 15 hours to make it to one of the five main endings of Warden of the Coast. The mod's story will kick in after you finish The Way of the Voice quest, though there's an option to begin sooner if you want to get right into it on a fresh save. Though you should be aware it's balanced for characters who are at least level five.
A planned update will make it possible for any of the companions from Warden of the Coast you romance to become a potential marriage partner after you finish the mod's questline. TheBawb notes that, after applying the update, "players will not need to replay the quest for the changes to be applied." You can find Warden of the Coast on NexusMods (opens in new tab). You won't need any other mods installed for it to work, though it is incompatible with The Great City of Solitude (opens in new tab) and Redbag's Solitude (opens in new tab).