Within the GameEx Arcade Edition Setup Wizard > Online Game Services > Steam, you can see the settings I use:
This is all I have setup for accessing games in Steam and they load without an issue. This is also a new PC with a recent Steam and games installation. You may have to sign in initially with MFA on the same machine, but going forward it should not matter.
GameEx_Start.._Steam_60_60_ 2023-11-19 19-25-16.mp4
Unfortunately, Windows video recording would not capture my game launch from the Steam menu, but I have had no problems launching a game with these settings without Steam loaded in the task tray or from PC startup. Also, you probably need to be connected to the internet to access Steam and launch the games.
As for the references to a steam.ini file, that was likely an older thread for setting up Steam as a separate emulator prior to the integrated Steam settings.