From what I understand, there's a file in the CAM (and the SPAM that's not incompatible with both the NAM and CAM) that interferes with the NAM, but as long as the NAM loads after the CAM, you're solid.
When SC4 starts up, it loads everything in your plugins folder in alphabetical order. Typically the usage of "ZZZZZ" in a filename is so that it overwrites something else that modifies the same thing. Most transit texture mods are like this. Conversely, the use of "!!!!!" will make a file load first.
Back to the issue with a specific CAM-related file that interferes with the NAM's own files. What you have there are two files that overwrite the same thing, and when that happens, typically the file that loads last is the one that will work in-game. Typically, things you want to load after the NAM are transit textures, and the things you (might) want to have load before it so that they're overwritten are traffic simulators that interfere with the NAM itself. Why is this a problem? The NAM has specifically-designed traffic simulators that not only increase capacity, but also make certain other plugins (such as the NWM and RHW) work properly. The fact that the CAM has its own simulator means that using it instead of the NAM's may result in dysfunctional networks.
Additionally, the CAM does have a few of its own buildings, but they're re-lotted versions of the default buildings so that they have higher growth stages and capacities. That's merely a handful of buildings, and there are a lot of growth stages to fill up.
What the CAM does (and similarly the SPAM) is merely modify the exemplars that control the number of growth stages, that's it. It has none of its own buildings, other than the re-lots. So yes, you have to go through a download spree if you want the most out of the CAM.
While I'm on the matter, the SPAM (SimPeg Agricultural Mod) does the same thing that the CAM does, but only for agricultural lots. It already comes with some of its own farms, which spares you from doing a large download spree. However, using that with CAMpatible (CAM-compatible) agriculture lots will cause undesirable effects with demand.
My recontamination to get the best out of the CAM: Avoid using its traffic simulator. Use the NAM's. Since, alphabetically, NAM loads up after CAM, that problem should be mostly avoided.
If you're going to use the SPAM, avoid downloading any CAMpatible agriculture lots, and unless you really want to, avoid its own traffic simulator.
I've found this to be the most ideal configuration: CAM, NAM, then SPAM minus traffic simulator.
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EDIT: I may be a bit iffy on what exactly in the CAM that may interfere with the NAM so to be on the safe side, ensure it loads before the NAM. I know for sure that something in the SPAM will definitely interfere with the NAM, so if you have that, have it load after the CAM but before the NAM.