Thank you Bits360!
That was indeed a stupid idea. Really don’t know why I thought the Cascade Shadows looked better in the first place. I changed that and also removed the other stuff like fog, clouds or background … just to be sure that these components aren’t influencing anything for now.
Foliage looks better now … but to be honest there is still room for improvement.
Is it even possible to get darker shadow areas inside an already existing shadow, like with the bushes underneath the trees?