The security systems have made a lot of changes in the last 10 years. Earlier models of NVRs only came with 4 or 6 ports so if you had more cameras than that you had to have a switch and a power insert for each camera or a POE switch.
I don't know if this has changed but if you plugged the camera directly into the NVR it took control of your camera. That includes IP addresses. Depending on your network you might want static IP addresses. At least with my current system if you want to login to the camera directly you had to have it on a POE switch. I will see how the new one is when I get it.
My current NVR has a recording capacity of 32 MBPS. The new one will have 10x that at 320 MBPS. The more cameras you add and the higher the MP the higher the recording capacity will be needed.
Many of the cheap NVRs you can buy online don't have the capacity to record all of the cameras they come with at the highest settings. As an example you get a great looking 12 3MP camera system but the NVR can only handle 80 MBPS. If you only connect 4 cameras you can record at 1080P /30fps but if you add more cameras you have to drop the resolution to 720p.
This link can explain it more.
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