Yes, I need to look into what
@GoodRevrnd was mentioning up there, because I never really modded Witcher 3. I assume that by "EE" it just means the extended edition, which is basically default? This really does need some HD texture overhaul (I don't recall some of the wooden wall textures, especially, being as awful as they are), and difficulty. Death March really gets way too easy, too fast.
Does the Steam workshop exist still? I was looking for that to make things easier, but looks like I might have to spend time with uh...crap what is the one that everyone uses? I can't remember off the top of my head.
W3 is a more difficult game to mod so there's no steam workshop report and even Nexus Mod Manager makes it a mess. Someone did develop a mod manager for the game, but it's generally best to do it manually or only use the manager for most of your graphics mods. Beyond that you also need to manage script conflicts between mods (esp gameplay ones) which is confusing af at first but not too difficult.
EE / W3EE is Enhanced Edition, which should really read more like Darksoul's Edition (from what I understand, never played DS). The biggest feature imo is completely overhauled combat. Dodging is more important and not full invulnerability, attack type differences matter more, and better granularity in strike distance and aiming. No levels--monster power is what it is, within some range, and you increase power via your skills and gear. Skill progression is semi-use based (you still allocate to skills by choice, but you earn the points in the 5 areas by performing actions related to them). Gear progression is defined more by addition of secondary stats than raw damage/armor (this was one of the weaker parts of the mod when I played, but they apparently completely rebuilt and rebalanced all gear since I played to make it more varied, interesting, and progressive), relics are completely unique and varied with interesting secondary effects. EE also packs in a lot of QoL mods or other mod features by default, like FriendlyHUD. EE is also extremely tunable via menus, so if it's too hard I would suggest just cranking your HP up, but there are a lot of other options.
GhostMode is basically default Witcher experience completely rebalanced and bugfixed. There is seriously no reason to play the game without this mod.
FCR3 was a dev-made overhaul. It has not been updated and there's no particularly good reason to use it over GhostMode.
I don't know anything about Redux.
None of the overhaul mods are compatible with save games so stop playing now and pick one.
Without going super deep, go grab HD Reworked, HD Monsters Reworked and maybe a lighting mod and you're good to go. I'd recommend ALM or PLM for lighting.