I have access to the devices, but I need remote access to change wallpaper, blocking rules, passwords. I would like to know if I can do this without the need for a physical server, and take advantage of the windows licenses that they already have. Sorry if I wrote something incomprehensible.
You can by using the native remote desktop application, you just need to add yourself as someone who has permissions to do so and enable said permissions. You also need be on the same network physically or via VPN.
With that said, the rest are third party or paid options, unfortunately.