I am worried that there is not really a benefit of doing that, just more noise and energy consumption.
I’m not sure that I understand the “more noise and energy consumption” part, since we’re still talking about the same router with the same connected devices.
But I do have multiple SSIDs on my router. One is explicitly for IoT devices, and they don’t have network access, so they are isolated from my computers, NAS, etc.
The more SSIDs being broadcast the more airtime is wastes on broadcasting them. SSIDs are also broadcast at a much lower speed so even though it’s a trivial amount of data, it takes longer to send. You ideally want as few SSIDs a possible but sometimes it’s unavoidable, like if you have an open guest network, or multiple authentication types used for different SSIDs.
Is there a measurable, real-world effect? Because if so, I don’t see it, and I can max out my router’s bandwidth pretty easily without noticing any slowdowns (this is with 30+ devices across three different SSIDs).