How will the video capture card work in my case?

Question

Iron

Hello. I can not understand something in the operation of video capture devices.
Monitor 4K 144Hz.
Let's say I take an external device. For example AVERMEDIA TECHNOLOGIES LGP LITE
The device has an HDMI port. But everything works for me on DP. There is no desire to connect a monitor via HDMI. Accordingly, the question, having DP and HDMI outputs on the video card, can I connect the main monitor to DP, the capture device to HDMI, put "duplicate monitors" in the system. Set the desired resolution for the capture device, and thereby get both the monitor and the stream through the capture device? How will this affect the load on the system?

Second, I will take a PCI card. For example AVERMEDIA TECHNOLOGIES LIVE GAMER 4K GC573
Does the monitor need to be connected to a video capture device? Or, again, you can plug it into the video card, and put the capture device as a "copy" of the monitor. Is it necessary to plug the wire into the device into the IN port (and the PCI slot is used only as a power supply)? Or the device can work on a PCI slot? Just again, it only has HDMI and I need DP. And secondly, it does not pull 4K 144Hz.
I will also have a garter for the stream of two webcams. Does this need to be done through third-party software and "be friends" with video capture software, or how is it tied up?
Streaming without a video capture device is problematic, as you understand, the load on hardware with such a monitor is not weak anyway. And if you also install software for streaming ...

Answer 1

In a well-established system, video compression is handled by the video card, so you don't need a capture device, but a good card with a hardware codec and properly configured software. The video from the webcam is also already compressed - for mixing, again, you need to use a video card - it will decode, mix and encode the mixed video back, along with the frame captured directly from the video memory.
A good piece of software that supports hardware encoding and mixing is obs-studio. Practice on it, and then run to spend money.
I do not see the need to use a video capture device in this case.