So did Curze wear gauntlets then to cover his hands/fingers? Because in the pictures shown when he is hunting/torturing Vulkan he has gauntlets on with sharp points to the fingers. Are you sure he used his bear hands? And not just gauntlets sharped to the razor sharp points?Lux. Thank you for asking such an insightful question.
It's been established in Unremembered Empire that Curze does not use lightning claws other than for ceremonial purposes. In the text, during his massacre of the Space Wolves detachment, we see him use his claws and nothing else. If I recall correctly, he would sharpen them in between combat on the ceramite helms of defeated enemies.
This explains your statement regarding his claws being able to move independently like fingers.
Again in the aforementioned text, we see Curze discard his Mars-issued armor and don the armor of his defeated enemies. However, given the size disparity between a Primarch and an Astartes, Curze would often have to stretch the ceramite material using his prodigious strength in order to cover any revealed portions on his body.
Also I would think that curze had a special suit of armor particularly crafted for his size, because it one of the books it mentions he has a specially crafted helm that augments his vision.