To host a server, you need to use the -dedicated flag when you start MM. Then it won't open up a UI, and will just host the server. Everyone who connects to the server can edit options in the lobby, per usual. The options will be saved on the server. Things like blind deployment and preventing local saves are game options that you can edit in the lobby. You can also set a server password so only those with the password can change game options. Also, once you have the game options you want, the game options dialog has the options to save the options to an XML file. That way, if anyone changes the options later, you can just reload them. Changing the amount of RAM really depends on how large of a game you want to run. It can't hurt to allow more RAM to be used. I feel like anything over 2GB is overkill.