passt problemlos

Yup fits. I have also installed it like this ✌🏼

Should not be a problem. However, the Nvme slots are no longer accessible once the graphics card has been installed. Resp. you have to remove the graphics card to access the slots. But you can use them.

As you don't change your Nvme SSD every day, it should be no problem, as mentioned.

I don't know which plugs you mean. I don't see a problem. The card is not so wide that it reaches to the bottom of the board.