Question about Icy Box IB-MS505-TI

On top of each other no, portrait mode is possible.

No. This bracket really only allows 3 monitors in a roughly horizontal arrangement.
The middle bar is too short to arrange two monitors on top of each other. The two outer swinging arms are attached to the middle bar with only one component and the individual height adjustment of the swinging arms is approx. +/-15cm, which is also not sufficient even if both are set to the highest and lowest position respectively. Another problem would be that the table clamp would be loaded asymmetrically, which is not what it is designed for.