I have a hard time believing that they will say anything, or even find out about an LSD or aftermarket clutch/flywheel (unless the clutch pedal is super heavy of course) so I wouldn't be too worried about those three things atleast.
Coilovers needs TÜV certification, recent alignment papers, and headlight adjustment. Height obviously needs to be withing the limits specified by TÜV.
As for seats and cage, I think you'll have to ask SV about this, even if they're a bit slow at replying. But I suspect they will require TÜV for this as well.
Full cage is probably not legal, unless it just requires bolstering near your head. 🤔