You recommend to remember which mod replaces files and which doesn't...To frequently check updates for all installed mods and download them manually for each mod...To have several copies of the game for all my possible purposes, and remember what exactly I've changed in each one?...
That's why I said in an organized manner which you have to do once. You don't have to remember anything. I organize things for all games that I mod even when I use mod-managers for large games, it's just a good practice which I also do for saves.
I don't know about you but I have tons of other normal/degen stuff to play, I don't have time to play KP after every minor update, so I don't update mods after every update either, I wait until major updates.
I have 2 separate copies of the game, vanilla, and modded + CCMod. I used to have another copy for modded without CCMod but now I just use my batch script that I originally made for GTA V and modified it for KP to toggle all mods on my vanilla copy.
I don't know why you persist of having to remember which is which as if you don't have the ability to name the folder to your liking.
...I understand how it can be seemingly easier to install mods by copy/pasting them in the folder, but it's error prone and irreversible process...
I don't see how a simple DragNDrop is more "error prone" than mod managers which is more likely to cause user end problems
(especially when coomers don't read instructions) or "irreversible"when most mods in KP are non-replacers and it also doesn't take time to reinstall a mere 2GB game if you do somehow mess up with replacers.
If you use the mod manager for other games as well then I guess you have a reason to make use of it
(although I've personally moved on from NMM a long time ago even before KP). Otherwise it's unnecessary for most people that just use it for KP unless if you obsess over having the game/mods updated after every minor release.