how do they work exactly they come on by them selves or do i have to run a switch and operate manually?

Actually, there is an approximate loss of close to 30% in the drivetrain in the ram. That would mean that if there is a gain of 10HP at the wheels then there is approximately a 14HP increase at the flywheel.
If in fact there is only a 10HP increase at the flywheel then there will be a 7HP increase at the rear wheels.

I havent seen anything on a dyno but there is an assumed gain of 7-10HP at the rear wheels.

i plan on doing efan soon. will it be fine leaving in stock stat or is 180 required?

The stock thermostat will be fine. You just have to adjust your fan controller to come on just before the halfway mark on the temp gauge. With the 180 tstat, you can adjust the fan controller to cut on at a lower temperature (around 175 I think).