ML350p and 2nd Media Bay Cage Kit

Hello to all

We recently purchased an used ML350p G8 SFF from another company.
We need to use drive 3.5", so we have to buy a LFF bay.

Now these are our questions:
1. The second media bay cage is always usable or need second processor?
2. The second media bay cage (661618-B21) is different from the primary drive cage (659485-B21) or are they interchangeable?

Thanks in advance for your attention,
Daniele