I can give some examples of my grid.
A big benefit to having a dedicated file server is that no matter what "terminal" I sit at, I always see the same desktop and files. I can sit at my desk with drawterm on a Linux workstation, or in bed with drawterm on a Windows laptop, or using a raspberry pi as a bare metal 9Front terminal.
CPU server doesn't have to mean number crunching. I have a raspberry pi cpu server that has a sensors hooked to it, and runs a file system to send commands to smart lights. And another that has sensors and displays simple data using an led grid. I made a kind of router using an old Dell and a used 4 port nic, and it is technically a cpu server, in that it has no monitor or keyboard and boots off the file server.
As a learning experience, having separate file/cpu/terminal is nice because you can actually practice integrating them on a network. However, if you are trying to do this out of a university dorm, then I could see things being so cramped that running a bunch of computers to kind of do 1 thing would seem overly complicated.