How to calculate channel width for RDP?

Question

RDP

Tell me how to correctly calculate the channel width with the following input data:
10 users.
Connection to the server via OpenVPN
There are no forwarded printers, but there are network printers that are connected to a remote server. The channel is not heavily loaded with printing, they practically do not print large documents. Yes, little by little.
The lion's share of the channel is eaten up by the transmission of sound over RDP (sip-softphones). Sound is used by 5 users.
Optimization of OpenVPN and RDP is done by virtue of knowledge, but it's better to discount it. Yes, just in case.

Answer 1

and for OpenVPN use
UDP Fast I/O -Use fast I/O operations with UDP writes to tun/tap