Coilover is a type of assembly that has the coil
over the strut ... basically it is a single object that serves the purpose of a strut & spring combination
example:
those are the least expensive model you can get for a 3rd Generation Camry ... upwards of $850ish
the ride height is fully adjustable, as well as Camber (wheel angle off the center line created from front-to-back) and a few other settings .... this means you can bring your Center of Gravity way down, but Ride Comfort can be greatly comprimised
for your purposes, a good strut & spring combo would be best it sounds like ...
Good Struts:
-KYB GR-2s

-Tokico HPs
the KYB GR-2s will be stiffer than OEM/Factory struts ... but the Tokico's will be the most stiff
there are a slew of springs you can get, depending on if you want a modest drop or a huge drop ... for a modest drop, the springs i would recommend are as follows:
- Eibach
- H&R Sports (or H&R OE Sports if you dont want much of a drop at all)
what you see in my signature is the Tokico Suspension Kit, which i am purchasing because it comes with both Struts & Springs ... which i like, because of warranty issues, and that way you know the springs were made for the struts they sit on, but you shouldnt have problems with any combination