I used to run a gaming server(s) for about four years, we peaked at about 3500 registered users, with 200 concurrent users.... We used Mumble in the community before I came along, we ran Mumble, after I came along, I took over the server and hosted it on a 1 core, 512mb memory linux server.... never went above 2% cpu and... I forget, probably 150MB memory usage with no restriction on quality (users can transmit CD quality audio)... this worked great, I set it up in about 10 minutes with little experience at the time, and the mumble server ran for years without issue until someone dictionary attacked the password.
Big advantages:
1. Free
2. Very low resource requrements, even for hundreds of users. Probably runs great on a google micro-f1 (Free forever) instance
3. Crystal clear audio
4. Lots of in-game plugins, such as positional audio in game (Battlefield: Bad Company 2, you could hear your teammates talking as they came up the stairs behind you, etc)
5. Cert based identity management. Used private key auth to verify you were you; no other user could sign in and impersonate you. Certified users had a big yellow C next to their name.
Probably the biggest thing for me, is that there was never, ever an audio glitch where the computer was not able to send/receive audio. We regularly run in to audio problems in Meet/Hangouts where audio does not work properly.
When I looked in to online gaming a couple of years ago I was stunned to see that everyone had moved to Discord, I didn't see the advantage of "upgrading" to something with a web client, but I suppose there's less friction to using a web client, even if mumble is a very easy install on Windows.
