Ah, my mistake, "-localPath" is actually specific to the game I'm working on. Looking at it, it's local by default. If you specify parameter -app "name", it will use that "name" as the folder name in My Documents -- so you were doing it right.
Btw, server.dat will only have something in it if you actually save RFCs -- meaning you have to use persistent channels as well.
The admin.txt file should get generated if it's not there, but it's done only when you launch a server instance from within your game iirc. It's like that because it automatically adds the local user as the administrator.