Good Day,
In your deployment are you looking for clarity on Internal webRTC users or external webRTC users connecting to your CMS's?
If internal, clients can talk directly to the CMS Web bridge and call bridge so there would be no need for a Exp E or C or TURN services.
If you are looking to connect external webRTC users then its recommended you use a Expressway E & C pair as both a web proxy and TURN server. There is no need to configure the turn service on the CMS itself as you will add the Expressway-E as TURN server onto the CMS.
You can find more information here:
https://www.cisco.com/c/en/us/support/docs/conferencing/meeting-server/210800-configure-cms-webrtc-proxy-over-expressw.html
Also note that Cisco plans to remove the TURN server component from the Cisco Meeting Server software in a future version so its best to start your setup with TURN using Expressways.
Hope this helps,