Ok ill list some essentials off but first gotta ask do u have a pretty decent geared PC?
Download jsawyer mod, fook, fook-jsawyer patch, vurts dead wasteland version, delay dlcs, burnman retex, nvinteriors, interior lighting overhaul, warzones, project Nevada core only, populated casinos, Mojave nights, electrocity, no npc compass, uncut strip open, uncut outside debts, uncut a Wilder wasteland, nights are darker, uncut freeside open.
Those will make the game alot challenging and harder but doable at hardcoe settings and on very hard, plus makes game look better and adds ALOT of uncut material because either consoles couldnt handle them or well ya basically that lol. Also adds tons of game fixes as far as bugs, glitches, and other things like ghouls giving no karma gain instead of vanilla giving alot of good karma killing them.
Id also recommend NV bounties as a very well done and challenging fan made quest mod.
Also recommend using nmcs texture then overwriting with poco burnish then overwriting with NV-terrain recreational project hd v02.
Music I recommend Mojave music radio and all 4 music packs.
That should be a great list there to be complete with any mods u may need, that list will do the job as making it difficult, adding lore weapons and armor, fixing bugs and glitches, and provide incredible immersion.