How to set Steam options from a batch file?

I repair computers and often need to reconfigure or reinstall the software. Some users want Steam installed. I have a batch file that installs all the requested / required apps, including Steam. Steam has the ability to set various options from within its GUI, but that requires logging in. Besides, setting things through a GUI violates the whole idea of a batch file: run just one file and let it automatically do everything that’s needed with no further operator interaction.

I found out how to keep Steam from auto-launching by running the following command after Steam is installed:

REG DELETE "HKEY_CURRENT_USERSOFTWAREMicrosoftWindowsCurrentVersionRun" /V "Steam" /F

But I need to set several other parameters / options as well. Logging into Steam to get to the GUI is simply not an option. How can I set things from the batch file?