Hello,
Currently I am looking at setting up a server for a not for profit organization so that we can block nasty things (phishing etc) and I discovered Pi-hole. My understanding that Pi-hole only works on DNS. I have taken this for a quick test at home and I like the user interface and how it blocks ads.
Does anyone know if this can be extended so that I can see what taking place, like who been ftp, torrent etc? Also would this give the same protection as a UTM?
Thank you 
Pi-hole only has DNS logs and those alone won't tell you what protocols were being used like FTP / Torrents or anything. DNS logs just tell you <x> network client wanted to go look up what IP <y> site was. Pi-Hole just blocks unwanted DNS lookups by redirecting them to it's own blocked page. It's up to you to determine what lists you include so you can block more than ads for additional network safety, if you choose to; by default pi-hole is just ads though.
To answer your topic question, no pi-hole is not a proxy and probably never will be. Squid is an example of web proxy software, several products have built on top of squid to enable a safer web experience based off block lists by category, similar to pihole's dns lists. There's also non open source security proxy products out there. Web proxies and squid are a completely different category of product / service. The level of detail you're asking for in terms of what protocols are being used would require a pretty advanced proxy, more than just squid since squid is just for web.
Thank you for the advice @diginc, what I might end up doing is starting with pi-hole and see where we end up. We could end up adding many sites to the block list if we see that site is using too much data (and users shouldn't be accessing that site).
While I would only get the domain name from the log, at lease I can see what site someone been accessing.
Sounds like a good plan. I did see there are quite a few privoxy posts around this forum which you may want to use in your research if you decide you did need something beyond pi-hole.
https://discourse.pi-hole.net/search?q=Privoxy (and of course google)