There are OEM shaped "lowering springs" that are made to fit stock-like struts. These springs look like inverted cones, essentially. Then, there are "coilover springs" that have the same diameter throughout the entire length of the spring.
You can't use "coilover springs" with the Bilsteins because there is a fixed lower spring perch that only accepts OEM shaped "lowering springs".
Coilovers have a threaded shock body with an adjustable lower perch that is usually machined to accept a variety of "coilover springs".
Even the V3's have their downfalls. the shop I use refuses to sell them to anyone. It is a bad choice of springs rates. And they seem to be more unreliable than other competitors.
If you read around, the people that track their car with V3's have either done the Swift conversion, or still don't like the handling.
For you, I think the Bilsteins and Eibach/BMW Performance springs would be a great choice.