I think mine said 1.25-1.5" drop, I noticed about 1.25" They do make a noticeable difference.
I think they are a little soft as far as spring rates go
The Ground control kits use adjustable sleeves, I don't know the spring rates. You can run them at pretty much whatever height you want.
I am working on a custom rear coilover suspension for my Grand Prix to delete the stock monoleaf, the parts are not expensive to build a kit yourself.
The struts are pretty standard diameter so threaded sleeves are avaialable, I think the important thing is grinding the spring perch off and installing a proper length spring. The GC runs sleeves atop the existing perch, the front springs end up being under 8" IIRC
I ran a $60 set of Civic coilovers on my Capri for a while. Way too stiff, was a backbreaking ride. The spring size was "too tall" and thus even at the lowest adjustment on the sleeve, I was at stock ride height. No lowering was possible without getting a shorter spring