I don’t like ARC due to possible security issues. Last thing I need is a third party opening up a port in my firewall they leave open to goodness knows what. I know my IoT devices do the same but they aren’t running a full OS capable of anything.
In terms of logging in/out your Roon server stays on 24/7. You really only login once to validate your credentials. For this reason it’s good to do some research and get the lowest wattage mini/micro PC you can. Sometimes this is an old laptop running Linux.
In addition to Windows, Roon server runs under MacOS, or Linux but not under Linux/ARM. Also recommend you connect it via Ethernet, as all audio streams in and out will flow through the server.