Hey there...
First things first....bp2008 is the man, and better than most at zeroing in on the sweet spot (frames per second/data rate). The calculation he's doing relates to just how much total data the CPU has to process at any given time and the one you are describing should work just fine. In my experience, finding that sweet spot is the biggest part of the battle. In my case, I've got 35 cameras of varying resolutions from 1080p PTZ's, to several 4K cameras. I have found that by "selectively" modifying each camera's parameters, I can achieve the results I'm looking for. For example, I prioritize frame and data rates for specific cameras that I want to very closely monitor. The others I will dial down to a set of "it works" parameters that give me enough visual information to make it useful, but save the heavy lifting for the cameras that matter most.
The only other thing I can add here is that from my own experience, the more cores/threads your processor has, the better the performance in high-camera-count situations. I am currently running an Intel i9-7980XE with 18 cores and 36 threads. Through much experimentation (and a lot of help from guys like bp2008), I have determined that core count really helps! This is of course based solely on my own experience, so your mileage may vary
Hope this helps!
