There are many threads discussing lowering springs, probably the most recent here
I had my 2006 NC Sport lowered by 30mm with the Eibachs in 2000 by Wheels In Motion and wouldn’t go back to the longer springs. In my opinion the wheels look better in the wheel arches and the handling improved. I get no trouble with clearance on speed bumps. I’ve also fitted firmer door bushings (again, lots of discussion on the boards) which I feel firm up the car.
Regarding bump stops; I’ve left mine as is and only very occasionally feel the springs bottom out on them at speed on rougher roads.
Edit: Just looking at your original post, you mention Eibach Pro-Sport coils which are progressive. I don’t know if the ones WIM fitted are linear or progressive - I’ll have to check now.
Definitely worth getting a proper 4 wheel alignment done afterwards though, whatever you do.