Apple has removed the ability to manage File Sharing, Time Machine and Caching within Server 5.4 on macOS High Sierra. This, IMHO, is bad news for system administrators. I do hope Apple change their minds on this and put these features back in the Server app. Perhaps this is a sign that Apple no longer want to support servers on Macs.
An excellent alternative to macOS Server is Synology DiskStation with it’s brilliant DSM 6.1 OS.