With everything routing through the same server, a heavy load should affect all feeds the same (in other words, if the bedroom camera for their apartment is jumpy, the kitchen camera for another apartment should be equally jumpy). The server is in effect taking the very small bandwidth pipeline out of the camera and rebroadcasting it out on a large bandwidth pipeline. Now, it is possible that a camera operating in IR mode requires more bandwidth than one that is not, which would cause there to be bandwidth issues on the apartment end. But that's where proper active load balancing would come into play. When a camera suddenly starts using higher bandwidth, load balancing would fix the problem.
Look at it this way - we'll use 3 cameras for example:
UNBALANCED BANDWIDTH:
CAM 1 - USING 1MB/S - ALLOTTED 1.5MB/S
CAM 2 - USING 1MB/S - ALLOTTED 1.5MB/S
CAM 3 - USING 1MB/S - ALLOTTED 1.5MB/S
TOTAL - USING 3MB/S - ALLOTTED 4.5MB/S
This would be what ideal bandwidth allotment would look like. No issues with video here.
CAM 1 - USING 1MB/S - ALLOTTED 1.5MB/S
CAM 2 - USING 2MB/S - ALLOTTED 1.5MB/S
CAM 3 - USING 1MB/S - ALLOTTED 1.5MB/S
TOTAL - USING 4MB/S - ALLOTTED 4.5MB/S
Here, Cam 2 has a spike in bandwidth required to stream properly. However, there is no load balancing, so even though the camera needs 2mb/s to stream properly, it's only getting 1.5mb/s to use. You're going to get lag on Cam 2 as a result - that's your choppiness and artifacts.
LOAD BALANCING ENABLED:
CAM 1 - USING 1MB/S - ALLOTTED 1.25MB/S
CAM 2 - USING 2MB/S - ALLOTTED 2MB/S
CAM 3 - USING 1MB/S - ALLOTTED 1.25MB/S
TOTAL - USING 4MB/S - ALLOTTED 4.5MB/S
Here, when Cam 2 has a spike in bandwidth required to stream properly, the router with load balancing will adjust to allow the required bandwidth to flow through properly. No lag in the feed.
Note, that in all three examples, the total usage and allotment of the bandwidth doesn't change. But, because there's active load balancing, it changes per camera to ensure that the feeds flow through properly.
Also, if by chance all three cameras were to increase their total usage higher than their total allotment, one of two things would happen. On an unbalanced load, you'd get lag on all three cameras. On a balanced load, depending on the configuration, you'd either get lag on all three cameras or you'd have one or two cameras without lag and two or one cameras without lag.