Keep in mind that these type of cameras, although are spec'd and capable of these various parameters, real world testing shows if you try to run these cameras at 30fps and high bitrates that you will max out the CPU in the camera and then the camera bugs out just long enough that you miss something. My car is rated for 6,000RPM redline, but I am not gonna run it in 3rd gear on the highway at 6,000RPM...same with these types of cameras - gotta keep them under rated capacity. Some may do better than others, but you are running the CPU higher. Surprised you haven't ran into issues, or maybe you have but unaware...
Look at all the threads where people came here with a jitter in the video or IVS missing motion and they were running 30FPS and when people tell them to drop the FPS and they dropped the FPS to 15FPS the camera became stable.
So it would be reasonable to assume that too many users coupled with higher FPS and bitrates will be problematic.
I thought I remember reading somewhere that it is best to stay under 3 concurrent. But lowering FPS or resolution, etc. can certainly help in this regard.