Here’s a thread from a few years ago. It has some information on RTCM3 data rates to compare with:
You could also measure for yourself what the data rate for each message is. For example, enable one message on your Reach M+. Then with a Linux box, connect to M+ and measure the output using the netcat and pipeviewer programs.
Example:
nc 192.168.2.15 9000 | pv -trai 0.1 > /dev/null
The options -trai 0.1 make the output like this: Total data, elapsed time, instantaneous bit rate, average bit rate.
There are different netcat (nc) versions. Yours may require different options. Substitute 192.168.2.15 with the IP address of your M+. For this test, the M+ base mode should be configured to output RTCM3 as a TCP server on port 9000.