If you’ve bought the hardware (DSCS9) and Xibo for Android licences then all you need now is a monitor/screen to connect the DSCS9 to it. The monitor itself does not need to be a smart TV, it just needs HDMI so you can connect your android device (DSCS9).
Regarding CMS, we usually recommend a VPS with Ubuntu 16.04 LTS 64 server to set up a docker Xibo instllation - CMS Installation Service
But you can opt to use different solution, you also not necessarily need to use docker (it is just recommended), instructions and requirements for various methods are here - https://xibo.org.uk/manual/en/install_cms.html
Server specification will highly depend on number of displays, will the stats be enabled, what log level will you use, what collection interval will displays use, how often will they need to download new content, how much content will you have etc
ie it’s hard to guess how big load there will be on the server without any details.
I’d suggest installation that can be easily scaled if necessary to ensure it will be suitable in case you will need it.