Questions about BlackMagic Intensity Pro 4K setup

Hi,

I am willing to buy the BlackMagic Intensity Pro 4K -capture card, but there are still a few things which I am confused about. My setup will a following:

Main Computer (Windows10), which have BlackMagic Intensity Pro 4k, running Resolume Arena 6.
Second computer (windows10), running a realtime visualisation software, of which screen I want capture to the Arena. I will use HDMI cable between computers.

1. Which computer thinks that it has two monitors? - The second computer which is sending the video or the main computer which is receiving that. I am now thinking about options for Windows Display settings.

2. Can I extend my second computers screen or is mirroring the only option?

3. Do I need Blackmagics own software to make things work or will Resolume recognize video input immediately.

- Thanks for a great software and a community!

The Intensity card is not a screen card, it will not be seen as such.
AFAIK from a friend who is using Resolume, it's using a codec that's not recognised by DR. Rather use BM's Desktop Video or OBS for recording.