What you need to determine first is the springs manufacturer drop claim.
What 3 series version are the springs for?
That gives you the starting point, and then any spec drop would be from the factory ride height.
Is it for a standard base, luxury line, modern line?
If so, then it will drop that ride height by 20-25mm from standard.
That would mean that if you installed those springs on any F30 version, including sport/Msport, the drop would be the same for all of them,
20-25mm.
If the springs are for an sport/Msport line, then the 20-25mm drop would be in addition to the factory ride height for the sport/Msport.
That would mean the overall drop would be 30-35mm lower than a base, luxury, or modern line.
That's because the sport/Msport are already 10mm lower than non sport/Msport lines.
So you have to know which F30 version is the basis for the springs claimed drop.
The difference in Kg could be for front and rear.
The 328i is close to 50/50 weight distribution front to rear.
The 335i is not as close to 50/50, there is more weight up front.
So, you'd likely want a slightly stiffer spring up front compared to the rear.
Since the front to rear weight difference isn't huge for the 335i, then the spring rate difference won't be as large either.
To be sure ask the manufacturer for the specifics relating to your BMW.
