Ethernet switches might be capable of 15,000 to a million packets per second. I do not think 24 packets (12 requests, 12answers) will stress it very much. But this is not a networking performance advice forum.
Whether you have to do this polling, or you can instead set up your cameras to send unsolicited messages in response to real events is a function of your cameras capabilities. There are only the two ways to do this.
Buy better a normal camera that sends movement by itself without polling (read - with support of motion detection by OH)
Realy to say, Reolink does it, but it do not supportted by OH, so you need to poll it.
There is a topic in Community.
Search for something like ip camera binding. The biggest one. The is a list of compatible cams like dahua and so on.
Nativly reolink support it in onvif, but this binding do not work with it. I tested it for half year, maybe now smth changed. Read that thread.
I believe something has changed as we have a few users of reolink now using the binding.
The cameras with the most features are the ones that are both api and Onvif. This post Linked below breaks it down. I would not go for a non onvif camera as you gain a lot by having this as a bare minimum.