They are separate SSID's and separate subnets, so for example my main network has addresses on 10.10.1.x and my streaming is 10.10.4.x and my IoT is 10.10.8.x.
I obviously have a bit of networking experience, but even if I didn't it still would have been pretty easy. There is a huge community online and on Reddit for help. The UDM can route traffic so certain things get where they need to be and you can further lock down the stuff you don't want. My Plex server is on the .4 network and my printer is on the .1 network but I can still print from the server to that printer.