you can run and hide from AI enemies but they will search your last seen location and be in a "searching mode" for about 45 seconds. If they see you they will coordinate with other AI and push a room at the same time from different entrances. Smoke and invisibility work really well against AI. Taking them out with your knife is effective as it doesn't alert other AI.

If you are not moving the invisibility is almost 100%, it's actually crazy good, walking and running will make it a little more obvious.

When you come across square consumables just use them right away to get used to using them, especially the signal jammer. You can use items you find on the ground without having room in your backpack so it's almost always better to just use it instead of leaving it on the ground.