The security cameras only remove 1% of level security for each destroyed. The computer nodes, if I recall correctly, remove about 10% of level security for each one destroyed.
So once you find and destroy all the computer nodes on Level 1 (I think there are six, all in the same room), you will see the level security drop drastically.
As for starting weapons:
Pipe - Use to bash service droids and mutants about the head to conserve ammo.
Stungun - Useless. Bin it.
Dartgun - Use needle darts. 5 darts should take down a standard cyborg drone. Later in the game (when you reach the pods) this can be useful again.
Sparq - Great weapon (one fully charged shot can down cyborg drone), but recharging is a drag. So I tend to save it for Cyborg assassins until I get the...
Pistol - THIS IS THE DADDY OF LEVEL 1! Found in the computer node room, which is why I make a beeline there. Use stadard ammo on organics, and teflon (Armour Piercing) ammo on robots/cyborgs (Teflon gets a damage bonus against cyborgs but a penalty against organics).
The pistol will be your 'go-to' weapon for much of the game.
You should also have picked up:
Magpulse - Found in the supply closet in the medical zone. Unlocked in cyberspace from the jack nearby. Use this to take out the Cyborg Warrior (2 shots) guarding the Computer Nodes, and also the few hoppers on this level as they have high armour.
The Magpulse will be your 'boss killer' until you get:
Magnum - Possibly the best weapon in the game, and available from level 1! Although, you won't find very much ammo early in game. It's located in a cupboard in the 'crew's last stand' area (the part that's crawling with Cyborg Assassins), but you can't get it until you reduce Level 1 security to 0%.
This is all from memory, so can't be 100% of the accuracy!
Hope that helps
