>>717210179 (OP)
>Is there anything else I should know before playing
Get the GEP gun from Paul, the other weapons he offers can be looted from enemies.
Lethal weapons like knives and firearms always make your enemies scream, even if you sneak up and kill them in one blow.
Tranq bolts for the crossbow never put an enemy to sleep in one hit so they will always be alerted to your presence as will any enemy standing near them.
Knocked out enemies never wake up.
Picking up NSF bodies in Clinton Castle is the same as killing them so leave them be until you finish the task.
You can increase the damage of your weapon by 80 times if you stand really close behind enemies and headshot them with a gun.
The game is pretty stingy with experience points but having most skills at untrained and trained level doesn't lock you out of content. You should only bother upgrading your preferred weapon skill to master level.
Playing non-lethal only changes some NPCs dialogue 90% of the time, so play however you want.
Microfibral Muscle isn't needed to access an area that can't be entered from another way.
Plasma weapons are bugged and deal really low damage.
You can climb up walls by putting LAMs, gas grenades, anything you can place on walls.
>which difficulty is the best for a first playthrough
Depends on your skill, but the game isn't hard if you sneak around. If you are being one-tapped frequently on realistic difficulty by mooks with 10mm pistols then lower it. Difficulty only affects melee, firearm and turret damage the enemies deal.
