Here's the post I made a few days ago about what mods I use, and I'll add some comments about lower end hardware alternatives/settings. Too lazy to get links, just search for them at Nexus.
Optimized Vanilla Textures(Low end: Instead try Texture Optimization Project or Wasteland 512. NOTE - These WILL decrease visual quality. Only use if you're already planning to turn down texture settings in the launcher, or you'd rather turn up other options and deal with lower quality textures. See screenshots/videos on the mod pages for exactly how much it changes. Wasteland 512 has a link to some suggested ini file changes too. Can't really help you with this since I don't use any of it.)
Vivid Fallout - Landscapes(Low end: Choose the 1k textures, or don't use at all.)
Vivid Fallout - Rocks(Low end: Choose the 1k textures, or don't use at all.)
FAR - Faraway Area Reform(Should be a quality increase with no performance hit.)
FogOut(I use indoor only. If you want outdoors too, pay attention to the next mod's installer.)
Darker Nights(no darker than Medium, because of the next mod below -- I use Light with the anti-cheat thing for sneak at level 4 as well. Vanilla sky. Choose to install compatibility patch for FogOut only if you use outdoor version, not needed for indoor only.)
Fr4nsson's Light Tweaks(Formerly known as Realistic Lights. Shouldn't have a performance hit, might increase fps due to removing some light/shadow sources.)
Ceano's SweetFX - RL(edited to remove SMAA and tone down lumasharpen because they fuck up the game's text horribly, and remove Bloom because bloom is garbage and it has a pretty significant performance hit too. Low end: Definitely do not use Bloom or SMAA. In-game FXAA is what you want. AMD users avoid TAA unless very high end hardware.)
FPS dynamic shadows - Shadow Boost(this mod dynamically adjusts your shadow rendering distance based on current FPS. Low end hardware will need to edit the ini and set desired fps to something more realistic, or just not use it at all since you may never be able to turn shadow draw distance above the minimum.)
And make sure you get theSimple Bug Fixesmod. Nothing to do with visuals, but it fixes a bunch of bugs that Bethesda is being as slow as ever about releasing a patch for. Some will probably never be fixed if previous games are any indication.