I recently discovered TK Dodge RE and True Directional Movement. They make close combat feel so much better that I finally want to play a melee character. (And they're not too demanding for relatively low spec hardware.)

The SimonMagus616 mechanic overhauls, collectively known as Simonrim, have caught my interest most recently. They seem very focused on improving the vanilla experience without unbalancing the game. There are about a dozen mods in the series, covering things from perk trees to encounter zones. All of them are linked near the bottom of the Adamant page.

The EnaiSiaion mechanic overhauls, collectively known as Enairim, lie on the other end of the spectrum . It has been years since I used one, but as I recall, they prioritized spectacular power over balance. They're all linked near the bottom of the Ordinator page.

This is quite tough, personally if anyone want tos try out an expansive amount of Skyrim mods I recommend Wabbajack. It allows you to install modlists that are quite expansive and well put together. I used to manually mod my Skyrim back in the day but this is leagues ahead of what I could ever have done.

For singular mods/adds

ENB Boris, the guy in charge of this is a Russian reactionary dude who has some very unkind thoughts about anyone who is not straight. He can be a massive asshole at any and all times. The problem with this is however how brilliant ENB is, anytime you have ever seen a hyper modded great looking Skyrim it's not just the 4k textures doing the heavy lifting. I guarantee it's ENB that really makes it pop out. I really wish Boris would just idk calm down and chill out, but it doesn't seem likely. You can like the work without supporting the artist of course but just keep this in mind about him.

Project AHO Arguably my favourite quest mod for Skyrim, if you liked Morrowind and felt Solstheim wasn't really scratching that itch then you might love this. It really harkens back to old 3rd era Morrowind, the basics of the story is that there is a settlement of House Telvanni, Sedrith Kegran, hidden in Skyrim. You are enslaved and brought there and then begin to work your way up finding out that Sedrith Kegran is attached to a Dwemer ruin with a powerful Dwemer device of some kind powered by Aetherium. I love this mod for many reasons but mainly the setting, story and rewards. This mod is quite kind with what it offers you, which is imo fair because this mod also demands a sacrifice from your character. As a slave you won't be leaving Sedrith Kegran easily any time soon, so it order to justify the lack of freedom and time spent the mod offers great rewards.

Clockwork Another quest mod, I try not to spoil much about this one but the brass tacks is you head through a passage in the Velothi mountains upon reading the note of a treasure hunter/bandit that attacks you. All is not as it seems. Warning whilst this mod is generally quite a normal romp through Skyrim, it demands isolation, no companions, and the first part of the mod can be quite scary. It's the best attempt at horror I've seen in Skyrim to this day and I've played a fair few mods in my time. But honestly give this one a shot, it comes with a great home as a reward at the end.

I’m probably in the minority but I really dislike SkyUI, it’s so immersion breaking for me and looks too ‘modern’. So since SkyUI is a prereq for many popular mods, I always install something like Hide SkyUI to sort that for me.

I really enjoy additional armor sets to add variety to the world, specifically sets that look like they belong in Skyrim and match the aesthetic.

Using a combination of the creation club Alternate Armor mods, and Armor Variants Expansion is a favorite of mine.

AVE is similar to the Creation Club Alternate Armors, they're the same sets with new appearances, so with both combined each type of armor has a lot more variation in what can appear without impacting game balance or the aesthetic.

Whenever I downloaded Skyrim, Enairim was always a staple in my modded games. Enai’s mods are so cool and they really provide a lot of replayability and even some roleplaying if you're into that

Although it's more of a total overhaul, I've been a fan of Requiem. It's more of a traditional RPG overhaul, returning to a static level based system (i.e. enemies do not scale their levels with you and will be much more dangerous at low levels). The time commitment of compiling a good modlist and setting up and debugging the mods has discouraged me from playing it recently though.

I have recently been very much into follower mods! My current favorite is Xelzaz, an Argonian member of House Telvanni. I like the commentary he provides, as well as the utility. He will make you potions and meals if you ask for them, as well as mixed drinks while in a tavern. He has a quest related to crimson nirnroot that I enjoyed, and he has a short quest to get him a guar to ride! I have heard that he has a lot of interactions with Neloth on Solsthiem, but I haven't gotten around to the Dragonborn DLC in this playthrough yet since I wanted to defeat Alduin first and complete the civil war questline for once before that.

I also have a lot of character customization mods: RaceMenu, Total Character Makeover, KS Hairdos, Improved Eyes, Apachii Divine Elegance, Wolfpaint, and Simple Belly Paints. I don't use any body changing mods though because I play on a laptop and when I tried using HIMBO it wrecked my preformance to the point it was unplayable.

I really love Beyond Skyrim: Bruma Its a bit of a demo release of the whole Beyond Skyrim project, but it has lots of new items, quests, dungeons, etc. Also some of the best voice acting i've seen from any mod.

I'm by no means a core skyrim player - I've never played through the story - but I love mods that improve the sandbox aspect of the game.

So: Frostfall for basic survival mechanics (that don't suck)
A new start-live another life - you're not the dragon born. You're just some dude.
Wearable Lanterns - immersive af
Diseased - improves on diseases and afflictions
Inconsequential NPCs - adds some more life to the world
Civil War battlefields and civil war overhaul redux and/or skyrim at war reborn - adds random npc battles, old battlefields, armies marching, and some more mechanics around the war that's supposed to be ongoing in the world around you.
True storms / other full weather overhauls - what it says on the tin.
Also there are some really cool companion mods that add quest lines about their background as you progress.

I always get Legacy of the Dragonborn. It's fun to have a museum to collect stuff in and it brings in some steady gold. It also has its own quests you can do.

Alternate start: live another life - is a must to skip the intro wagon scene

Rich skyrim merchants - Can pick how rich they are. Makes it easier to sell the stuff I hoard all at once

Khajiits steal too - Allows the Khajiit caravans to buy stolen items

If you aren't already aware, there's a dedicated Skyrim mods community over at skyrimmods@lemmy.world. (EDIT: Though I realize this community isn't accessible to those on Beehaw because of the defederation 🙃)

But to answer your question - I've been using Populated Skyrim: Hell Edition in my latest playthrough, and it's awesome how much more alive the world feels. Plus, having more bandits and adventurers on the road makes for some pretty awesome spontaneous encounters.

I also love skyrimlazz's castle mods for late-game dwellings.