To verify the exact performance that you can expect from NoMachine and determine how many clients can be reasonably run over the network connection you are planning for the deployment, you should proceed by running a sample NoMachine session and verifying the real bandwidth usage by means of the statistics.
To retrieve statistics, run the menu panel within the session by Ctrl+Alt+0 or clicking on the page peel. Click on Connection, then click on 'Take the statistics' and save them.
You should also ensure that the exact applications that you want to run are tested.
The numbers near the end of the 'NX Server Side Protocol Statistics' listing, just after the line reporting the protocol compression ratio, will tell you the bandwidth that the session is using, for example:
3452 B/s average, 961 B/s 5s, 4215 B/s 30s, 19509 B/s maximum.
The numbers are in bytes per-second.