I think it's like reducing their field view.
If they can see you 100 hexes unsneaked, they will see you in 50 hexes sneaked in front, so basic tactics and speed (Silent Running perk) still apply, as well as avoid facing their front FOVs and especially snipers with high PE.
...
Raise it to the 300% before you can take Ghost perk. Then, take it multiple times. It's safer.
Ah, btw, is a mine interieur considered technically a 'poor lighted area?'
what crack are you smoking that you can take multiple perks once sneak is at 300? that's pretty much every skill point for a 10 int character. Not to mention you can only take ghost once, and its not a one time addition of 30 skill points like thief, its a floating 30% bonus at all times. So whatever your sneak skill is you add 30%. Also i don't think the fonline engine has light/darkness in it. Nightvision doesn't work for this reason. From what I understood its a 30% bonus whenever you sneak, that's it.
Anyways the info i need isn't there, I need to formula for the check to see if sneak succeeded. I'm assuming its a roll v pe but without the numbers I won't know how much sneak is required.