MoCA setup diagram and Questions

I am looking for confirmation on a seemingly very simple internet setup with my Xfinity internet. I am curious if using MoCA will be possible in my scenario.

Per my diagram provided, I have two possible questions: (modem does not have MoCA technology)

1) Do I need two MoCA adapters in my current scenario? i.e. One adapter between the splitter and the upstairs Modem, and a Second adapter downstairs.

2) Or, do I only need 1 MoCA adapter, which i would put downstairs?(I have provided two diagrams. The first is my "current" setup. The second is the proposed two MoCA setup)

I think where I am getting confused, is does both MoCA devices talk to each other in the proposed setup, or do they need a dedicated coax line between them via another splitter in order to function properly?

Of course if this is not the right question to be asking here, please let me know, and/or delete this post. thank you!