what do the stats even do?

[Ghoul Thing One]

Can't find any description, and spending points doesn't seem to change anything. EDIT: Turns out if you boost vitality, health only increases if you change levels/die. Still don't know what most of the stats do.

[Shurik]

Yeah, they just wanna for us to test every stat on life action.
I didnt leveled up every one to see changes, but from my understanding it looks like this, and its simplified just from obvious changes you see on screen, and again - just speculations on some, so dont take my word on it in full:
Vitality - increases your health points.
Strength - your weight to carry stuff, gear and weapons
Perception - maybe how far you could detect items on the floor to pickup, also maybe connected to seeking enemies in some way.
Speed - your speed, lmao
Agility - thats a tricky one. there are famous flesh rats that can give toxicity, so with leveling it might decrease the amount of toxin you gain from hits, but to see real difference you need to level it up very good
Bioenergy - idk, really, there is DNA mutation you gain after each leveling up, maybe they connected?
Luck - maybe more money from enemies, for now loot from them is static, you gain weapon they wielded against you 100% after you kill them, and i dont know for now any other aspects of the game it affects.
Lack - looks like a joke, but someone will figure it out.

[giant rat]

agility makes you jump higher.
lack lowers your level by 1, which means you can level up for 2000€ (1000€ for a point in lack, 1000€ for the actual skill point).

personal insufficiencies are the meta when it comes to reichian psychoanalysis, it seems.

[Signfelled]

Perception makes your gun center on the screen faster