You can use one of your nodes as an exit node for another device and route your traffic though it as an alternative to a public VPN, depending on your needs.
I use it for remote management, video streaming, and the occasional file transfer without publicly exposing my NAS. You could achive all this by setting up your own wireguard server but that’s more work.
I’m surprised you’re finding it too slow for video streaming. I use it just fine and can saturate my 300 Mbit connection when doing file transfers.
Plants do indeed use O2. They use if for the same reason we do, the have mitochondria that use O2 during respiration.
During the day plants typically produce more O2 than they consume, but at night they need it from elsewhere.