Sometimes, enemies throw smoke grenades, meaning I can't see or target them (without help), but can they see me back? Does it affect their targeting/aim at all?
Yes, they can and will still continue to target/fire.
Be alert when moving through the smoke, as enemies will continue to fire through it, and the positions and numbers of enemies on the other side can change dramatically.
I do not have any specific details on if it affects their aim, but I doubt it does.
Yes, because they are simply AI, and know your whereabouts at all times whether or not there is smoke or a wall between you and them. This goes for any game that includes enemies. If the enemies are computer controlled/AI they will always know your current location, although they might not react that way.