Suggestion as a first test, before the expense of an NVR:
Wire your PC to the router.
Start the browser and connect to the Live View of the first camera.
Start another browser instance (not another tab) and connect to the Live View of the second camera.
Repeat for the remaining cameras.
Assuming the PC doesn't run out of resources, CPU and RAM, the idea would be to pull an increasing number of video streams over the network.
OK, not quite the same as an NVR pulling RTSP streams, but broadly similar, and maybe lighter than pulling the mainstream over RTSP.
I'm not sure if VLC allows multiple instances, but if it does, using RTSP with it would be a better match.
My expectation would be that the WiFi network would start to struggle as you start pulling video from an increasing number of cameras.
But easy enough to do, and may be an interesting result.