In theory most mods should be fine for singleplayer (there might be the occasional server-focused mod that maybe doesnāt work right, and game-balance on some might be aimed at group play, but thatās about it).
Hereās a list of some Iāve used in singleplayer (not all together) - one or two may now be outdated, but Iāll try to highlight those. Mostly I just look at the file sizes and then try to limit myself a bit so Iām not using too many different mods at once and not using too many big mods at once.
ModControlPanel - provides easier admin control access for a couple of mods (notably LBPR, Better Thralls and ThrallSidekick)
Cinnamon Candle - makes candles produce candlelight (rather than just being a flame that emits no light) Very small mod, but getting old, and might be out of date
Better Thralls - allows multiple followers, followers can drag bound thralls etc
ThrallSidekick - works very well with Better Thralls, summon specific followers to you, teleport followers back to their preset āhomeā spot. Also getting old. I know at least one server admin still using it, but it is one that could go wrong at some point.
Fashionist - reskinning armor and weapons, altering thrall appearances etc
Emotes for Thralls - system for getting followers and crafters to perform emotes (actually two systems, since followers work one way, crafters work another)
Arena Pier - great build set, plus adds a bunch of stuff like 2x2 gates. spiral stairs, half stairs, shallow roofs, iron bars build set etc
Northern Timber - four full build sets, all amazing
Limestone building - white limestone versions of the three base build sets
Savage Steel - ton of placeables, including a bunch of usable storage options like jars, barrels, crates, sacks etc
Immersive Armor - fantastic range of armor variants and adjusted versions of the base game armors - especially good with fashionist, since you donāt need to worry about the stats (though theyāre much more balanced than they were anyway)
LBPR Additional Features - snappable versions of workstations, bunch of additional storage and decorative options, really great ātavernā build set (fairly neutral colours which makes it good for internal walls because it has some double-sided walls and can go with most things)
Less Building Placement Restrictions - just basically essential
Pythagoras Support Beams - allow a bunch of cool building tricks - can be used to extend support over a wider area, but also to add snap points for positioning eg pillars differently
Kerozards Paragon Levelling - a decent levelling mod that shifts the cap to 300, but doesnāt feel too fast or overpowered (though any time you go above 60 the āopā issue can begin - Iām quite enjoying not having a levelling mod this time. But if you want one, Iād say this is a good one)
Waystones - buildable placeable teleport points - I found it made Siptah a lot more bearable to build my own āobeliskā network
Better Healing Arrows - again one Iāve stopped bothering with, but still good - sets healing arrows back to their old way of working so they can actually be useful for healing thralls.
Age of Calamitous - massive overhaul mod with magic etc - very cool, extremely tough and grindy for singleplayer
Age of Calamitous RP Add-on - reduces the grind a bit, but I still found I had to adjust settings a lot to find a balance that wasnāt too brutal
Glass Constructions and More - very cool, lots of awesome building stuff, but a little out of date, so Iām not certain if itās still working (though I believe others are still using it successfully).
Emberlight - semi-overhaul mod - lots of changes to farming (makes it more interesting - but still has the problem of not really being needed - you can just get everything you could farm for and it probably takes less workā¦), cool new legendary weapons, appearance changing, lots of stuff
DryBuildingsIndoors - fairly new, not seen any issues with it yet, stops it raining indoors
Savage Wilds - whole new map, pretty damned awesome (some areas can be a bit brutal solo, but most of it is like having a whole new Exiled Lands)
I hope some of that is useful - happy to explain more on things if you need it 