I personally lowered mine with the full ACS suspension system ie springs struts shocks etc.

I found the improvement to handling was very good plus I still kept all my BMW warranty. (ACS is fully approved and fitted by BMW)

In respect of handling, lowering alone may or may not improve the handling. I cannot answer that from your post alone There are also a lot of much more knowledgeable people on this forum who can answer that question for you too.

But before I can give an opinion I would want to know the rest of your setup ie wheels, suspension etc and do you plan on changing any of these after you lower?