wlan and eth are network adapters in your raspberry Pi probably. Not subnets. Subnet is a range of IP addresses the router can use to give out IP addresses to devices. Basically, let’s assume that the router/the local network has only one subnet 192.168.1.0/24. This number means, the router can give out IP addresses from 192.168.1.0 to 192.168.1.254. If the router had two subnets, let’s say A: 192.168.1.0/24 B: 192.168.2.0/24 device on subnet A, would be able to talk to the device on subnet B.
Either way, in my opinion you’re overcomplicating things a lot for yourself. If you only wish to watch from home, on your couch, you don’t need reverse proxies, cloudflare and all that jazz. Docker and raspberry pi is enough. I can walk you through it if you want :)