What configuration should I have for 200 users including bandwidth?
I’m afraid that specification probably covers two orders of magnitude in processor load, and at least an order of magnitude in network bandwidth (actually you don’t say you are using a network at all, so may be an infinite range).
Whilst you shouldn’t really expect much more than advice to benchmark and possibly examples of what others have done, you need a lot more detail. Is this for shop floor communication, with infrequent use, or is this a purely telephone based call centre? Are you recording? Are you using high compression codecs? Can you make use of direct media? Are most calls user to user, or most PSTN to user, etc.
Do you imply 200 simultaneous calls or 200 registered users ?
oh and don’t forget blf/presence! if they want all users monitoring all users then that’ll drastically change the requirements. 64 core amd epyc could be considered reasonable with that…