If the only thing connected to the upstream POE switches are the cameras, then no need to make those managed.
If the final POE switch that is acting as hub will have other devices connected to it, then it might make sense to manage that switch so that you don't get hacked.
But if all that is going to be connected to the POE switches are the cameras and the NVR, then managed is probably overkill.
At the end of the day, it is simply digital data. As long as the NVR can "see" the IP address of the camera, it doesn't care if it is 32 POE switches or 12 or 2 or 1 big POE switch. As long as they are all connected together in some way so that it has a path to the NVR, that is all that matters.
Many camera networks are unsecure, even those installed by professionals. This guide gives basic instruction in how to secure a camera network from the most common types of attacks. Perhaps the most important rule of securing a computer network is to not forward ports to unsecure services...
ipcamtalk.com
The internet is a force of nature; no video surveillance system made was designed to be exposed to those forces.. NEVER FORWARD PORTS to your NVR or Cameras, doing such things not only exposes you to severe security problems, but everyone else on the internet too.. Hackers dont want your video...
ipcamtalk.com