Maby there is a way to track the send packages with a TCP/IP monitor,
to actually check how much data per second the server has to transmit...

Anyways, the way you try to optimize your updates depends on how many clients on average should
join, how much the server should controll, and how often the updates should reach the client.

If you plan to make a shooter-type game with 4 Players over LAN, you can really let 3dGS
handle everything by default, as in LAN it it quick enough.

If you plan to "really" make a RPG with lets say 50 clients joining the server,
dont use the default way 3dGS is handeling the updates.

Get the more complicated way, and disable automatic updates.
Stuff your updates into variable arrays. (Maybe use arrays of different sizes,
to send the smaller arrays, if there are not that many updates)

This way you can even send the arrays to specific clients (var_send_to ....)
The sever needs to calculate then what each client is able to see,
stuff the updatedata into an array, and send it to the specific client.

This way you can manually limit the update packages to the required size.

Also try to use as many local entities on the clients as possible.
Any effects and ambient stuff, that do not affect the gameplay directly should be done on the client.
Also direct movement of client-players is somewhat tricky.
It would be too slow to just send movecommands to the server, and let the server move the player.
And on the other hand it yould be too unsecure to let the client move the player.

You need to find a tricky combination of these 2 methods,
to account for both speed and security.