Need some advice with network-centric builds

Hello everyone,

I want to have one machine that's both a router/firewall (I'm thinking pfSense) and a file server. The file server is one I would like to be accessible over the internet as well as over my local network, which is why I want to have its traffic go through a firewall.

So, are there any cases that can hold multiple mobos that I can use for this or do I have to get a small server rack and use the server chassis for this? If so, how many hard drives can they fit?

As for the file server part, is it possible to do something that acts like an FTP server over the web while acting as a NAS over the local network? My use of it over the web will be primarily to synchronize school files and whatnot (by that I mean backing up all my school work when I'm not at home then retrieving it when needed) while the local use would be general storage for media and the likes.

TL;DR: I am planning 2 builds, one as a router and one as a file server. Could they fit into one case? If not, what are good, space-efficient alternatives? Also, can the file server act as a simple NAS over the local network while being an FTP server over the internet?

Please advise.