i'm a noob also, but i can add some insight atleast.

1) you can "tune" your suspension. coilovers come with lots of adjustments, dampning settings, ride height, and spring rate. THe more expensive coilovers come with more adjustments, the cheaper ones come with presets. Usually a generic spring rate with a relative stiff dampning. If you buy springs from a company, most of the time they will allow you to choose your own spring rate. BUt yeah...tuning means you have to have access to a track and play with your settings over and over.

2) Well, most of the expensive ones allow you to change dampning settings. So you would select a softer setting for street, and harder setting for track. Tein makes EDFC which you can change many settings within the cabin. But on a daily driver, i would imagine one would just set-it and forget it. Atleast thats what i would do.

3) lowering your car will make your car handle better ( typcially) it lowers the cg.

4) Usually coilover dampners are harsh. They usually come with pillowball metal topmounts...which means there is no give between your suspension and your chassis. They usually are accompanied with a loud clunk's and creaks. Springs/shock combos usually retain stock topmounts so its a easier ride.

this is my generic philosophy,

daily driver no roadcourse or autoxing = spring/shock combo
daily driver w/occasional autoxing, roadcourse = coilovers
track slut = coilovers