Blanc, if you search you will find info on the LWFW.
Feedback is polarizing, nobody disputes the benefit in performance, however some believe it can cause the crankshaft to fail and to avoid this the clutch flywheel and crank should be balanced as a unit, to achieve this the crank needs to be removed from the car.
I do not yet have a LWFW, but have been looking into it and will have one fitted when my engine is upgraded this winter. - Hartech mentioned that they feel reducing the weight of the flywheel on the crankshaft can only be a good thing, but that it needs to be balanced and from what I can gather 9E & RPM think the same, however as with every upgrade there are those that disagree.
Szlard, did you have you LWFW balanced with the crank etc?
Wavetrack is an ATB not an LSD, if you google the difference between ATB & LSD the differences will be explained. - Both have pro's & con's.
The Wavetrack ATB claims to be able to help a little under breaking, where other ATB's, Quaife as an example do not.
Does your car have PSM?
Personally I do not feel a 996 struggles for traction on track, perhaps a little out of slow corners where you can spin up the unload wheel, but its not significant and IMHO this is not something i have ever noticed on the road.
Due to this I have procrastinated about the benefits of an ATB, the rear of the car moves around more under braking so I feel a plate LSD would be beneficial in alleviating this but that brings a heap of additional maintenance issues, ATB is maintenance free.
I appreciate all of the above does not answer your questions but I hope it at least provides a little more info.
As a side note, the cheapest way to add performance and improve braking & handling is to remove weight.