In my experience, the Arlo Cameras won’t do anything when Arlo is in Disarmed mode state. The Cameras must be On and in an Arlo Armed mode state for SmartThings to trigger a recording.
So I just leave Arlo set in Armed mode, and then have SmartThings turn On/Off the cameras depending on the SmartThings Armed status. Example, if SmartThings is Disarmed, I have SmartThings turn all of the Arlo Cameras Off so they don’t do anything even though Arlo is set to an Armed mode state. If SmartThings is Armed Away, I have SmartThings turn all of the Arlo Cameras On so that SmartThings can trigger recordings since Arlo is in an Armed mode state.
BTW, here’s a big thread about the latest SmartThings Arlo Schema.