Here is a brief description of my experience with Lane Keep Assist on my 3.6 SE w/Technology:
If the system detects that you are in a lane and the vehicle drifts, the vehicle will automatically steer the car to keep it in the lane. If the system detects that you are in a lane and you attempt to steer the vehicle outside the lane without the turn signal on, you will feel resistance in the wheel as the vehicle attempts to stay in the lane but ultimately, your steering input will override the auto steer and this will briefly inactivate the lane keep assist until it detects you are in a lane again. The only sound warning is when the vehicle detects that you are not controlling the steering for a period of time, it will sound a warning and the display will tell you to take over steering.
With blind spot monitoring, if you attempt to steer the vehicle into a lane when it is indicating another vehicle is in your blind spot, the steering wheel will vibrate/shake rapidly as an additional warning to the blind spot indication in the mirror.
The system works great in my Atlas and I like it a lot. Hope this helps!